drm/panthor: Don't add write fences to the shared BOs

[drm/drm-misc.git] / arch / x86 / events / intel / pt.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Intel(R) Processor Trace PMU driver for perf
 * Copyright (c) 2013-2014, Intel Corporation.
 *
 * Intel PT is specified in the Intel Architecture Instruction Set Extensions
 * Programming Reference:
 * http://software.intel.com/en-us/intel-isa-extensions
 */

#undef DEBUG

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/bits.h>
#include <linux/limits.h>
#include <linux/slab.h>
#include <linux/device.h>

#include <asm/perf_event.h>
#include <asm/insn.h>
#include <asm/io.h>
#include <asm/intel_pt.h>
#include <asm/cpu_device_id.h>

#include "../perf_event.h"
#include "pt.h"

static DEFINE_PER_CPU(struct pt, pt_ctx);

static struct pt_pmu pt_pmu;

/*
 * Capabilities of Intel PT hardware, such as number of address bits or
 * supported output schemes, are cached and exported to userspace as "caps"
 * attribute group of pt pmu device
 * (/sys/bus/event_source/devices/intel_pt/caps/) so that userspace can store
 * relevant bits together with intel_pt traces.
 *
 * These are necessary for both trace decoding (payloads_lip, contains address
 * width encoded in IP-related packets), and event configuration (bitmasks with
 * permitted values for certain bit fields).
 */
#define PT_CAP(_n, _l, _r, _m)                                          \
        [PT_CAP_ ## _n] = { .name = __stringify(_n), .leaf = _l,        \
                            .reg = _r, .mask = _m }

static struct pt_cap_desc {
        const char      *name;
        u32             leaf;
        u8              reg;
        u32             mask;
} pt_caps[] = {
        PT_CAP(max_subleaf,             0, CPUID_EAX, 0xffffffff),
        PT_CAP(cr3_filtering,           0, CPUID_EBX, BIT(0)),
        PT_CAP(psb_cyc,                 0, CPUID_EBX, BIT(1)),
        PT_CAP(ip_filtering,            0, CPUID_EBX, BIT(2)),
        PT_CAP(mtc,                     0, CPUID_EBX, BIT(3)),
        PT_CAP(ptwrite,                 0, CPUID_EBX, BIT(4)),
        PT_CAP(power_event_trace,       0, CPUID_EBX, BIT(5)),
        PT_CAP(event_trace,             0, CPUID_EBX, BIT(7)),
        PT_CAP(tnt_disable,             0, CPUID_EBX, BIT(8)),
        PT_CAP(topa_output,             0, CPUID_ECX, BIT(0)),
        PT_CAP(topa_multiple_entries,   0, CPUID_ECX, BIT(1)),
        PT_CAP(single_range_output,     0, CPUID_ECX, BIT(2)),
        PT_CAP(output_subsys,           0, CPUID_ECX, BIT(3)),
        PT_CAP(payloads_lip,            0, CPUID_ECX, BIT(31)),
        PT_CAP(num_address_ranges,      1, CPUID_EAX, 0x7),
        PT_CAP(mtc_periods,             1, CPUID_EAX, 0xffff0000),
        PT_CAP(cycle_thresholds,        1, CPUID_EBX, 0xffff),
        PT_CAP(psb_periods,             1, CPUID_EBX, 0xffff0000),
};

u32 intel_pt_validate_cap(u32 *caps, enum pt_capabilities capability)
{
        struct pt_cap_desc *cd = &pt_caps[capability];
        u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
        unsigned int shift = __ffs(cd->mask);

        return (c & cd->mask) >> shift;
}
EXPORT_SYMBOL_GPL(intel_pt_validate_cap);

u32 intel_pt_validate_hw_cap(enum pt_capabilities cap)
{
        return intel_pt_validate_cap(pt_pmu.caps, cap);
}
EXPORT_SYMBOL_GPL(intel_pt_validate_hw_cap);

static ssize_t pt_cap_show(struct device *cdev,
                           struct device_attribute *attr,
                           char *buf)
{
        struct dev_ext_attribute *ea =
                container_of(attr, struct dev_ext_attribute, attr);
        enum pt_capabilities cap = (long)ea->var;

        return snprintf(buf, PAGE_SIZE, "%x\n", intel_pt_validate_hw_cap(cap));
}

static struct attribute_group pt_cap_group __ro_after_init = {
        .name   = "caps",
};

PMU_FORMAT_ATTR(pt,             "config:0"      );
PMU_FORMAT_ATTR(cyc,            "config:1"      );
PMU_FORMAT_ATTR(pwr_evt,        "config:4"      );
PMU_FORMAT_ATTR(fup_on_ptw,     "config:5"      );
PMU_FORMAT_ATTR(mtc,            "config:9"      );
PMU_FORMAT_ATTR(tsc,            "config:10"     );
PMU_FORMAT_ATTR(noretcomp,      "config:11"     );
PMU_FORMAT_ATTR(ptw,            "config:12"     );
PMU_FORMAT_ATTR(branch,         "config:13"     );
PMU_FORMAT_ATTR(event,          "config:31"     );
PMU_FORMAT_ATTR(notnt,          "config:55"     );
PMU_FORMAT_ATTR(mtc_period,     "config:14-17"  );
PMU_FORMAT_ATTR(cyc_thresh,     "config:19-22"  );
PMU_FORMAT_ATTR(psb_period,     "config:24-27"  );

static struct attribute *pt_formats_attr[] = {
        &format_attr_pt.attr,
        &format_attr_cyc.attr,
        &format_attr_pwr_evt.attr,
        &format_attr_event.attr,
        &format_attr_notnt.attr,
        &format_attr_fup_on_ptw.attr,
        &format_attr_mtc.attr,
        &format_attr_tsc.attr,
        &format_attr_noretcomp.attr,
        &format_attr_ptw.attr,
        &format_attr_branch.attr,
        &format_attr_mtc_period.attr,
        &format_attr_cyc_thresh.attr,
        &format_attr_psb_period.attr,
        NULL,
};

static struct attribute_group pt_format_group = {
        .name   = "format",
        .attrs  = pt_formats_attr,
};

static ssize_t
pt_timing_attr_show(struct device *dev, struct device_attribute *attr,
                    char *page)
{
        struct perf_pmu_events_attr *pmu_attr =
                container_of(attr, struct perf_pmu_events_attr, attr);

        switch (pmu_attr->id) {
        case 0:
                return sprintf(page, "%lu\n", pt_pmu.max_nonturbo_ratio);
        case 1:
                return sprintf(page, "%u:%u\n",
                               pt_pmu.tsc_art_num,
                               pt_pmu.tsc_art_den);
        default:
                break;
        }

        return -EINVAL;
}

PMU_EVENT_ATTR(max_nonturbo_ratio, timing_attr_max_nonturbo_ratio, 0,
               pt_timing_attr_show);
PMU_EVENT_ATTR(tsc_art_ratio, timing_attr_tsc_art_ratio, 1,
               pt_timing_attr_show);

static struct attribute *pt_timing_attr[] = {
        &timing_attr_max_nonturbo_ratio.attr.attr,
        &timing_attr_tsc_art_ratio.attr.attr,
        NULL,
};

static struct attribute_group pt_timing_group = {
        .attrs  = pt_timing_attr,
};

static const struct attribute_group *pt_attr_groups[] = {
        &pt_cap_group,
        &pt_format_group,
        &pt_timing_group,
        NULL,
};

static int __init pt_pmu_hw_init(void)
{
        struct dev_ext_attribute *de_attrs;
        struct attribute **attrs;
        size_t size;
        u64 reg;
        int ret;
        long i;

        rdmsrl(MSR_PLATFORM_INFO, reg);
        pt_pmu.max_nonturbo_ratio = (reg & 0xff00) >> 8;

        /*
         * if available, read in TSC to core crystal clock ratio,
         * otherwise, zero for numerator stands for "not enumerated"
         * as per SDM
         */
        if (boot_cpu_data.cpuid_level >= CPUID_TSC_LEAF) {
                u32 eax, ebx, ecx, edx;

                cpuid(CPUID_TSC_LEAF, &eax, &ebx, &ecx, &edx);

                pt_pmu.tsc_art_num = ebx;
                pt_pmu.tsc_art_den = eax;
        }

        /* model-specific quirks */
        switch (boot_cpu_data.x86_vfm) {
        case INTEL_BROADWELL:
        case INTEL_BROADWELL_D:
        case INTEL_BROADWELL_G:
        case INTEL_BROADWELL_X:
                /* not setting BRANCH_EN will #GP, erratum BDM106 */
                pt_pmu.branch_en_always_on = true;
                break;
        default:
                break;
        }

        if (boot_cpu_has(X86_FEATURE_VMX)) {
                /*
                 * Intel SDM, 36.5 "Tracing post-VMXON" says that
                 * "IA32_VMX_MISC[bit 14]" being 1 means PT can trace
                 * post-VMXON.
                 */
                rdmsrl(MSR_IA32_VMX_MISC, reg);
                if (reg & BIT(14))
                        pt_pmu.vmx = true;
        }

        for (i = 0; i < PT_CPUID_LEAVES; i++) {
                cpuid_count(20, i,
                            &pt_pmu.caps[CPUID_EAX + i*PT_CPUID_REGS_NUM],
                            &pt_pmu.caps[CPUID_EBX + i*PT_CPUID_REGS_NUM],
                            &pt_pmu.caps[CPUID_ECX + i*PT_CPUID_REGS_NUM],
                            &pt_pmu.caps[CPUID_EDX + i*PT_CPUID_REGS_NUM]);
        }

        ret = -ENOMEM;
        size = sizeof(struct attribute *) * (ARRAY_SIZE(pt_caps)+1);
        attrs = kzalloc(size, GFP_KERNEL);
        if (!attrs)
                goto fail;

        size = sizeof(struct dev_ext_attribute) * (ARRAY_SIZE(pt_caps)+1);
        de_attrs = kzalloc(size, GFP_KERNEL);
        if (!de_attrs)
                goto fail;

        for (i = 0; i < ARRAY_SIZE(pt_caps); i++) {
                struct dev_ext_attribute *de_attr = de_attrs + i;

                de_attr->attr.attr.name = pt_caps[i].name;

                sysfs_attr_init(&de_attr->attr.attr);

                de_attr->attr.attr.mode         = S_IRUGO;
                de_attr->attr.show              = pt_cap_show;
                de_attr->var                    = (void *)i;

                attrs[i] = &de_attr->attr.attr;
        }

        pt_cap_group.attrs = attrs;

        return 0;

fail:
        kfree(attrs);

        return ret;
}

#define RTIT_CTL_CYC_PSB (RTIT_CTL_CYCLEACC     | \
                          RTIT_CTL_CYC_THRESH   | \
                          RTIT_CTL_PSB_FREQ)

#define RTIT_CTL_MTC    (RTIT_CTL_MTC_EN        | \
                         RTIT_CTL_MTC_RANGE)

#define RTIT_CTL_PTW    (RTIT_CTL_PTW_EN        | \
                         RTIT_CTL_FUP_ON_PTW)

/*
 * Bit 0 (TraceEn) in the attr.config is meaningless as the
 * corresponding bit in the RTIT_CTL can only be controlled
 * by the driver; therefore, repurpose it to mean: pass
 * through the bit that was previously assumed to be always
 * on for PT, thereby allowing the user to *not* set it if
 * they so wish. See also pt_event_valid() and pt_config().
 */
#define RTIT_CTL_PASSTHROUGH RTIT_CTL_TRACEEN

#define PT_CONFIG_MASK (RTIT_CTL_TRACEEN        | \
                        RTIT_CTL_TSC_EN         | \
                        RTIT_CTL_DISRETC        | \
                        RTIT_CTL_BRANCH_EN      | \
                        RTIT_CTL_CYC_PSB        | \
                        RTIT_CTL_MTC            | \
                        RTIT_CTL_PWR_EVT_EN     | \
                        RTIT_CTL_EVENT_EN       | \
                        RTIT_CTL_NOTNT          | \
                        RTIT_CTL_FUP_ON_PTW     | \
                        RTIT_CTL_PTW_EN)

static bool pt_event_valid(struct perf_event *event)
{
        u64 config = event->attr.config;
        u64 allowed, requested;

        if ((config & PT_CONFIG_MASK) != config)
                return false;

        if (config & RTIT_CTL_CYC_PSB) {
                if (!intel_pt_validate_hw_cap(PT_CAP_psb_cyc))
                        return false;

                allowed = intel_pt_validate_hw_cap(PT_CAP_psb_periods);
                requested = (config & RTIT_CTL_PSB_FREQ) >>
                        RTIT_CTL_PSB_FREQ_OFFSET;
                if (requested && (!(allowed & BIT(requested))))
                        return false;

                allowed = intel_pt_validate_hw_cap(PT_CAP_cycle_thresholds);
                requested = (config & RTIT_CTL_CYC_THRESH) >>
                        RTIT_CTL_CYC_THRESH_OFFSET;
                if (requested && (!(allowed & BIT(requested))))
                        return false;
        }

        if (config & RTIT_CTL_MTC) {
                /*
                 * In the unlikely case that CPUID lists valid mtc periods,
                 * but not the mtc capability, drop out here.
                 *
                 * Spec says that setting mtc period bits while mtc bit in
                 * CPUID is 0 will #GP, so better safe than sorry.
                 */
                if (!intel_pt_validate_hw_cap(PT_CAP_mtc))
                        return false;

                allowed = intel_pt_validate_hw_cap(PT_CAP_mtc_periods);
                if (!allowed)
                        return false;

                requested = (config & RTIT_CTL_MTC_RANGE) >>
                        RTIT_CTL_MTC_RANGE_OFFSET;

                if (!(allowed & BIT(requested)))
                        return false;
        }

        if (config & RTIT_CTL_PWR_EVT_EN &&
            !intel_pt_validate_hw_cap(PT_CAP_power_event_trace))
                return false;

        if (config & RTIT_CTL_EVENT_EN &&
            !intel_pt_validate_hw_cap(PT_CAP_event_trace))
                return false;

        if (config & RTIT_CTL_NOTNT &&
            !intel_pt_validate_hw_cap(PT_CAP_tnt_disable))
                return false;

        if (config & RTIT_CTL_PTW) {
                if (!intel_pt_validate_hw_cap(PT_CAP_ptwrite))
                        return false;

                /* FUPonPTW without PTW doesn't make sense */
                if ((config & RTIT_CTL_FUP_ON_PTW) &&
                    !(config & RTIT_CTL_PTW_EN))
                        return false;
        }

        /*
         * Setting bit 0 (TraceEn in RTIT_CTL MSR) in the attr.config
         * clears the assumption that BranchEn must always be enabled,
         * as was the case with the first implementation of PT.
         * If this bit is not set, the legacy behavior is preserved
         * for compatibility with the older userspace.
         *
         * Re-using bit 0 for this purpose is fine because it is never
         * directly set by the user; previous attempts at setting it in
         * the attr.config resulted in -EINVAL.
         */
        if (config & RTIT_CTL_PASSTHROUGH) {
                /*
                 * Disallow not setting BRANCH_EN where BRANCH_EN is
                 * always required.
                 */
                if (pt_pmu.branch_en_always_on &&
                    !(config & RTIT_CTL_BRANCH_EN))
                        return false;
        } else {
                /*
                 * Disallow BRANCH_EN without the PASSTHROUGH.
                 */
                if (config & RTIT_CTL_BRANCH_EN)
                        return false;
        }

        return true;
}

/*
 * PT configuration helpers
 * These all are cpu affine and operate on a local PT
 */

static void pt_config_start(struct perf_event *event)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        u64 ctl = event->hw.aux_config;

        ctl |= RTIT_CTL_TRACEEN;
        if (READ_ONCE(pt->vmx_on))
                perf_aux_output_flag(&pt->handle, PERF_AUX_FLAG_PARTIAL);
        else
                wrmsrl(MSR_IA32_RTIT_CTL, ctl);

        WRITE_ONCE(event->hw.aux_config, ctl);
}

/* Address ranges and their corresponding msr configuration registers */
static const struct pt_address_range {
        unsigned long   msr_a;
        unsigned long   msr_b;
        unsigned int    reg_off;
} pt_address_ranges[] = {
        {
                .msr_a   = MSR_IA32_RTIT_ADDR0_A,
                .msr_b   = MSR_IA32_RTIT_ADDR0_B,
                .reg_off = RTIT_CTL_ADDR0_OFFSET,
        },
        {
                .msr_a   = MSR_IA32_RTIT_ADDR1_A,
                .msr_b   = MSR_IA32_RTIT_ADDR1_B,
                .reg_off = RTIT_CTL_ADDR1_OFFSET,
        },
        {
                .msr_a   = MSR_IA32_RTIT_ADDR2_A,
                .msr_b   = MSR_IA32_RTIT_ADDR2_B,
                .reg_off = RTIT_CTL_ADDR2_OFFSET,
        },
        {
                .msr_a   = MSR_IA32_RTIT_ADDR3_A,
                .msr_b   = MSR_IA32_RTIT_ADDR3_B,
                .reg_off = RTIT_CTL_ADDR3_OFFSET,
        }
};

static u64 pt_config_filters(struct perf_event *event)
{
        struct pt_filters *filters = event->hw.addr_filters;
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        unsigned int range = 0;
        u64 rtit_ctl = 0;

        if (!filters)
                return 0;

        perf_event_addr_filters_sync(event);

        for (range = 0; range < filters->nr_filters; range++) {
                struct pt_filter *filter = &filters->filter[range];

                /*
                 * Note, if the range has zero start/end addresses due
                 * to its dynamic object not being loaded yet, we just
                 * go ahead and program zeroed range, which will simply
                 * produce no data. Note^2: if executable code at 0x0
                 * is a concern, we can set up an "invalid" configuration
                 * such as msr_b < msr_a.
                 */

                /* avoid redundant msr writes */
                if (pt->filters.filter[range].msr_a != filter->msr_a) {
                        wrmsrl(pt_address_ranges[range].msr_a, filter->msr_a);
                        pt->filters.filter[range].msr_a = filter->msr_a;
                }

                if (pt->filters.filter[range].msr_b != filter->msr_b) {
                        wrmsrl(pt_address_ranges[range].msr_b, filter->msr_b);
                        pt->filters.filter[range].msr_b = filter->msr_b;
                }

                rtit_ctl |= (u64)filter->config << pt_address_ranges[range].reg_off;
        }

        return rtit_ctl;
}

static void pt_config(struct perf_event *event)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct pt_buffer *buf = perf_get_aux(&pt->handle);
        u64 reg;

        /* First round: clear STATUS, in particular the PSB byte counter. */
        if (!event->hw.aux_config) {
                perf_event_itrace_started(event);
                wrmsrl(MSR_IA32_RTIT_STATUS, 0);
        }

        reg = pt_config_filters(event);
        reg |= RTIT_CTL_TRACEEN;
        if (!buf->single)
                reg |= RTIT_CTL_TOPA;

        /*
         * Previously, we had BRANCH_EN on by default, but now that PT has
         * grown features outside of branch tracing, it is useful to allow
         * the user to disable it. Setting bit 0 in the event's attr.config
         * allows BRANCH_EN to pass through instead of being always on. See
         * also the comment in pt_event_valid().
         */
        if (event->attr.config & BIT(0)) {
                reg |= event->attr.config & RTIT_CTL_BRANCH_EN;
        } else {
                reg |= RTIT_CTL_BRANCH_EN;
        }

        if (!event->attr.exclude_kernel)
                reg |= RTIT_CTL_OS;
        if (!event->attr.exclude_user)
                reg |= RTIT_CTL_USR;

        reg |= (event->attr.config & PT_CONFIG_MASK);

        event->hw.aux_config = reg;
        pt_config_start(event);
}

static void pt_config_stop(struct perf_event *event)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        u64 ctl = READ_ONCE(event->hw.aux_config);

        /* may be already stopped by a PMI */
        if (!(ctl & RTIT_CTL_TRACEEN))
                return;

        ctl &= ~RTIT_CTL_TRACEEN;
        if (!READ_ONCE(pt->vmx_on))
                wrmsrl(MSR_IA32_RTIT_CTL, ctl);

        WRITE_ONCE(event->hw.aux_config, ctl);

        /*
         * A wrmsr that disables trace generation serializes other PT
         * registers and causes all data packets to be written to memory,
         * but a fence is required for the data to become globally visible.
         *
         * The below WMB, separating data store and aux_head store matches
         * the consumer's RMB that separates aux_head load and data load.
         */
        wmb();
}

/**
 * struct topa - ToPA metadata
 * @list:       linkage to struct pt_buffer's list of tables
 * @offset:     offset of the first entry in this table in the buffer
 * @size:       total size of all entries in this table
 * @last:       index of the last initialized entry in this table
 * @z_count:    how many times the first entry repeats
 */
struct topa {
        struct list_head        list;
        u64                     offset;
        size_t                  size;
        int                     last;
        unsigned int            z_count;
};

/*
 * Keep ToPA table-related metadata on the same page as the actual table,
 * taking up a few words from the top
 */

#define TENTS_PER_PAGE  \
        ((PAGE_SIZE - sizeof(struct topa)) / sizeof(struct topa_entry))

/**
 * struct topa_page - page-sized ToPA table with metadata at the top
 * @table:      actual ToPA table entries, as understood by PT hardware
 * @topa:       metadata
 */
struct topa_page {
        struct topa_entry       table[TENTS_PER_PAGE];
        struct topa             topa;
};

static inline struct topa_page *topa_to_page(struct topa *topa)
{
        return container_of(topa, struct topa_page, topa);
}

static inline struct topa_page *topa_entry_to_page(struct topa_entry *te)
{
        return (struct topa_page *)((unsigned long)te & PAGE_MASK);
}

static inline phys_addr_t topa_pfn(struct topa *topa)
{
        return PFN_DOWN(virt_to_phys(topa_to_page(topa)));
}

/* make -1 stand for the last table entry */
#define TOPA_ENTRY(t, i)                                \
        ((i) == -1                                      \
                ? &topa_to_page(t)->table[(t)->last]    \
                : &topa_to_page(t)->table[(i)])
#define TOPA_ENTRY_SIZE(t, i) (sizes(TOPA_ENTRY((t), (i))->size))
#define TOPA_ENTRY_PAGES(t, i) (1 << TOPA_ENTRY((t), (i))->size)

static void pt_config_buffer(struct pt_buffer *buf)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        u64 reg, mask;
        void *base;

        if (buf->single) {
                base = buf->data_pages[0];
                mask = (buf->nr_pages * PAGE_SIZE - 1) >> 7;
        } else {
                base = topa_to_page(buf->cur)->table;
                mask = (u64)buf->cur_idx;
        }

        reg = virt_to_phys(base);
        if (pt->output_base != reg) {
                pt->output_base = reg;
                wrmsrl(MSR_IA32_RTIT_OUTPUT_BASE, reg);
        }

        reg = 0x7f | (mask << 7) | ((u64)buf->output_off << 32);
        if (pt->output_mask != reg) {
                pt->output_mask = reg;
                wrmsrl(MSR_IA32_RTIT_OUTPUT_MASK, reg);
        }
}

/**
 * topa_alloc() - allocate page-sized ToPA table
 * @cpu:        CPU on which to allocate.
 * @gfp:        Allocation flags.
 *
 * Return:      On success, return the pointer to ToPA table page.
 */
static struct topa *topa_alloc(int cpu, gfp_t gfp)
{
        int node = cpu_to_node(cpu);
        struct topa_page *tp;
        struct page *p;

        p = alloc_pages_node(node, gfp | __GFP_ZERO, 0);
        if (!p)
                return NULL;

        tp = page_address(p);
        tp->topa.last = 0;

        /*
         * In case of singe-entry ToPA, always put the self-referencing END
         * link as the 2nd entry in the table
         */
        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
                TOPA_ENTRY(&tp->topa, 1)->base = page_to_phys(p) >> TOPA_SHIFT;
                TOPA_ENTRY(&tp->topa, 1)->end = 1;
        }

        return &tp->topa;
}

/**
 * topa_free() - free a page-sized ToPA table
 * @topa:       Table to deallocate.
 */
static void topa_free(struct topa *topa)
{
        free_page((unsigned long)topa);
}

/**
 * topa_insert_table() - insert a ToPA table into a buffer
 * @buf:         PT buffer that's being extended.
 * @topa:        New topa table to be inserted.
 *
 * If it's the first table in this buffer, set up buffer's pointers
 * accordingly; otherwise, add a END=1 link entry to @topa to the current
 * "last" table and adjust the last table pointer to @topa.
 */
static void topa_insert_table(struct pt_buffer *buf, struct topa *topa)
{
        struct topa *last = buf->last;

        list_add_tail(&topa->list, &buf->tables);

        if (!buf->first) {
                buf->first = buf->last = buf->cur = topa;
                return;
        }

        topa->offset = last->offset + last->size;
        buf->last = topa;

        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries))
                return;

        BUG_ON(last->last != TENTS_PER_PAGE - 1);

        TOPA_ENTRY(last, -1)->base = topa_pfn(topa);
        TOPA_ENTRY(last, -1)->end = 1;
}

/**
 * topa_table_full() - check if a ToPA table is filled up
 * @topa:       ToPA table.
 */
static bool topa_table_full(struct topa *topa)
{
        /* single-entry ToPA is a special case */
        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries))
                return !!topa->last;

        return topa->last == TENTS_PER_PAGE - 1;
}

/**
 * topa_insert_pages() - create a list of ToPA tables
 * @buf:        PT buffer being initialized.
 * @cpu:        CPU on which to allocate.
 * @gfp:        Allocation flags.
 *
 * This initializes a list of ToPA tables with entries from
 * the data_pages provided by rb_alloc_aux().
 *
 * Return:      0 on success or error code.
 */
static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp)
{
        struct topa *topa = buf->last;
        int order = 0;
        struct page *p;

        p = virt_to_page(buf->data_pages[buf->nr_pages]);
        if (PagePrivate(p))
                order = page_private(p);

        if (topa_table_full(topa)) {
                topa = topa_alloc(cpu, gfp);
                if (!topa)
                        return -ENOMEM;

                topa_insert_table(buf, topa);
        }

        if (topa->z_count == topa->last - 1) {
                if (order == TOPA_ENTRY(topa, topa->last - 1)->size)
                        topa->z_count++;
        }

        TOPA_ENTRY(topa, -1)->base = page_to_phys(p) >> TOPA_SHIFT;
        TOPA_ENTRY(topa, -1)->size = order;
        if (!buf->snapshot &&
            !intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
                TOPA_ENTRY(topa, -1)->intr = 1;
                TOPA_ENTRY(topa, -1)->stop = 1;
        }

        topa->last++;
        topa->size += sizes(order);

        buf->nr_pages += 1ul << order;

        return 0;
}

/**
 * pt_topa_dump() - print ToPA tables and their entries
 * @buf:        PT buffer.
 */
static void pt_topa_dump(struct pt_buffer *buf)
{
        struct topa *topa;

        list_for_each_entry(topa, &buf->tables, list) {
                struct topa_page *tp = topa_to_page(topa);
                int i;

                pr_debug("# table @%p, off %llx size %zx\n", tp->table,
                         topa->offset, topa->size);
                for (i = 0; i < TENTS_PER_PAGE; i++) {
                        pr_debug("# entry @%p (%lx sz %u %c%c%c) raw=%16llx\n",
                                 &tp->table[i],
                                 (unsigned long)tp->table[i].base << TOPA_SHIFT,
                                 sizes(tp->table[i].size),
                                 tp->table[i].end ?  'E' : ' ',
                                 tp->table[i].intr ? 'I' : ' ',
                                 tp->table[i].stop ? 'S' : ' ',
                                 *(u64 *)&tp->table[i]);
                        if ((intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) &&
                             tp->table[i].stop) ||
                            tp->table[i].end)
                                break;
                        if (!i && topa->z_count)
                                i += topa->z_count;
                }
        }
}

/**
 * pt_buffer_advance() - advance to the next output region
 * @buf:        PT buffer.
 *
 * Advance the current pointers in the buffer to the next ToPA entry.
 */
static void pt_buffer_advance(struct pt_buffer *buf)
{
        buf->output_off = 0;
        buf->cur_idx++;

        if (buf->cur_idx == buf->cur->last) {
                if (buf->cur == buf->last)
                        buf->cur = buf->first;
                else
                        buf->cur = list_entry(buf->cur->list.next, struct topa,
                                              list);
                buf->cur_idx = 0;
        }
}

/**
 * pt_update_head() - calculate current offsets and sizes
 * @pt:         Per-cpu pt context.
 *
 * Update buffer's current write pointer position and data size.
 */
static void pt_update_head(struct pt *pt)
{
        struct pt_buffer *buf = perf_get_aux(&pt->handle);
        u64 topa_idx, base, old;

        if (buf->single) {
                local_set(&buf->data_size, buf->output_off);
                return;
        }

        /* offset of the first region in this table from the beginning of buf */
        base = buf->cur->offset + buf->output_off;

        /* offset of the current output region within this table */
        for (topa_idx = 0; topa_idx < buf->cur_idx; topa_idx++)
                base += TOPA_ENTRY_SIZE(buf->cur, topa_idx);

        if (buf->snapshot) {
                local_set(&buf->data_size, base);
        } else {
                old = (local64_xchg(&buf->head, base) &
                       ((buf->nr_pages << PAGE_SHIFT) - 1));
                if (base < old)
                        base += buf->nr_pages << PAGE_SHIFT;

                local_add(base - old, &buf->data_size);
        }
}

/**
 * pt_buffer_region() - obtain current output region's address
 * @buf:        PT buffer.
 */
static void *pt_buffer_region(struct pt_buffer *buf)
{
        return phys_to_virt((phys_addr_t)TOPA_ENTRY(buf->cur, buf->cur_idx)->base << TOPA_SHIFT);
}

/**
 * pt_buffer_region_size() - obtain current output region's size
 * @buf:        PT buffer.
 */
static size_t pt_buffer_region_size(struct pt_buffer *buf)
{
        return TOPA_ENTRY_SIZE(buf->cur, buf->cur_idx);
}

/**
 * pt_handle_status() - take care of possible status conditions
 * @pt:         Per-cpu pt context.
 */
static void pt_handle_status(struct pt *pt)
{
        struct pt_buffer *buf = perf_get_aux(&pt->handle);
        int advance = 0;
        u64 status;

        rdmsrl(MSR_IA32_RTIT_STATUS, status);

        if (status & RTIT_STATUS_ERROR) {
                pr_err_ratelimited("ToPA ERROR encountered, trying to recover\n");
                pt_topa_dump(buf);
                status &= ~RTIT_STATUS_ERROR;
        }

        if (status & RTIT_STATUS_STOPPED) {
                status &= ~RTIT_STATUS_STOPPED;

                /*
                 * On systems that only do single-entry ToPA, hitting STOP
                 * means we are already losing data; need to let the decoder
                 * know.
                 */
                if (!buf->single &&
                    (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) ||
                     buf->output_off == pt_buffer_region_size(buf))) {
                        perf_aux_output_flag(&pt->handle,
                                             PERF_AUX_FLAG_TRUNCATED);
                        advance++;
                }
        }

        /*
         * Also on single-entry ToPA implementations, interrupt will come
         * before the output reaches its output region's boundary.
         */
        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries) &&
            !buf->snapshot &&
            pt_buffer_region_size(buf) - buf->output_off <= TOPA_PMI_MARGIN) {
                void *head = pt_buffer_region(buf);

                /* everything within this margin needs to be zeroed out */
                memset(head + buf->output_off, 0,
                       pt_buffer_region_size(buf) -
                       buf->output_off);
                advance++;
        }

        if (advance)
                pt_buffer_advance(buf);

        wrmsrl(MSR_IA32_RTIT_STATUS, status);
}

/**
 * pt_read_offset() - translate registers into buffer pointers
 * @buf:        PT buffer.
 *
 * Set buffer's output pointers from MSR values.
 */
static void pt_read_offset(struct pt_buffer *buf)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct topa_page *tp;

        if (!buf->single) {
                rdmsrl(MSR_IA32_RTIT_OUTPUT_BASE, pt->output_base);
                tp = phys_to_virt(pt->output_base);
                buf->cur = &tp->topa;
        }

        rdmsrl(MSR_IA32_RTIT_OUTPUT_MASK, pt->output_mask);
        /* offset within current output region */
        buf->output_off = pt->output_mask >> 32;
        /* index of current output region within this table */
        if (!buf->single)
                buf->cur_idx = (pt->output_mask & 0xffffff80) >> 7;
}

static struct topa_entry *
pt_topa_entry_for_page(struct pt_buffer *buf, unsigned int pg)
{
        struct topa_page *tp;
        struct topa *topa;
        unsigned int idx, cur_pg = 0, z_pg = 0, start_idx = 0;

        /*
         * Indicates a bug in the caller.
         */
        if (WARN_ON_ONCE(pg >= buf->nr_pages))
                return NULL;

        /*
         * First, find the ToPA table where @pg fits. With high
         * order allocations, there shouldn't be many of these.
         */
        list_for_each_entry(topa, &buf->tables, list) {
                if (topa->offset + topa->size > (unsigned long)pg << PAGE_SHIFT)
                        goto found;
        }

        /*
         * Hitting this means we have a problem in the ToPA
         * allocation code.
         */
        WARN_ON_ONCE(1);

        return NULL;

found:
        /*
         * Indicates a problem in the ToPA allocation code.
         */
        if (WARN_ON_ONCE(topa->last == -1))
                return NULL;

        tp = topa_to_page(topa);
        cur_pg = PFN_DOWN(topa->offset);
        if (topa->z_count) {
                z_pg = TOPA_ENTRY_PAGES(topa, 0) * (topa->z_count + 1);
                start_idx = topa->z_count + 1;
        }

        /*
         * Multiple entries at the beginning of the table have the same size,
         * ideally all of them; if @pg falls there, the search is done.
         */
        if (pg >= cur_pg && pg < cur_pg + z_pg) {
                idx = (pg - cur_pg) / TOPA_ENTRY_PAGES(topa, 0);
                return &tp->table[idx];
        }

        /*
         * Otherwise, slow path: iterate through the remaining entries.
         */
        for (idx = start_idx, cur_pg += z_pg; idx < topa->last; idx++) {
                if (cur_pg + TOPA_ENTRY_PAGES(topa, idx) > pg)
                        return &tp->table[idx];

                cur_pg += TOPA_ENTRY_PAGES(topa, idx);
        }

        /*
         * Means we couldn't find a ToPA entry in the table that does match.
         */
        WARN_ON_ONCE(1);

        return NULL;
}

static struct topa_entry *
pt_topa_prev_entry(struct pt_buffer *buf, struct topa_entry *te)
{
        unsigned long table = (unsigned long)te & ~(PAGE_SIZE - 1);
        struct topa_page *tp;
        struct topa *topa;

        tp = (struct topa_page *)table;
        if (tp->table != te)
                return --te;

        topa = &tp->topa;
        if (topa == buf->first)
                topa = buf->last;
        else
                topa = list_prev_entry(topa, list);

        tp = topa_to_page(topa);

        return &tp->table[topa->last - 1];
}

/**
 * pt_buffer_reset_markers() - place interrupt and stop bits in the buffer
 * @buf:        PT buffer.
 * @handle:     Current output handle.
 *
 * Place INT and STOP marks to prevent overwriting old data that the consumer
 * hasn't yet collected and waking up the consumer after a certain fraction of
 * the buffer has filled up. Only needed and sensible for non-snapshot counters.
 *
 * This obviously relies on buf::head to figure out buffer markers, so it has
 * to be called after pt_buffer_reset_offsets() and before the hardware tracing
 * is enabled.
 */
static int pt_buffer_reset_markers(struct pt_buffer *buf,
                                   struct perf_output_handle *handle)

{
        unsigned long head = local64_read(&buf->head);
        unsigned long idx, npages, wakeup;

        if (buf->single)
                return 0;

        /* can't stop in the middle of an output region */
        if (buf->output_off + handle->size + 1 < pt_buffer_region_size(buf)) {
                perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
                return -EINVAL;
        }


        /* single entry ToPA is handled by marking all regions STOP=1 INT=1 */
        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries))
                return 0;

        /* clear STOP and INT from current entry */
        if (buf->stop_te) {
                buf->stop_te->stop = 0;
                buf->stop_te->intr = 0;
        }

        if (buf->intr_te)
                buf->intr_te->intr = 0;

        /* how many pages till the STOP marker */
        npages = handle->size >> PAGE_SHIFT;

        /* if it's on a page boundary, fill up one more page */
        if (!offset_in_page(head + handle->size + 1))
                npages++;

        idx = (head >> PAGE_SHIFT) + npages;
        idx &= buf->nr_pages - 1;

        if (idx != buf->stop_pos) {
                buf->stop_pos = idx;
                buf->stop_te = pt_topa_entry_for_page(buf, idx);
                buf->stop_te = pt_topa_prev_entry(buf, buf->stop_te);
        }

        wakeup = handle->wakeup >> PAGE_SHIFT;

        /* in the worst case, wake up the consumer one page before hard stop */
        idx = (head >> PAGE_SHIFT) + npages - 1;
        if (idx > wakeup)
                idx = wakeup;

        idx &= buf->nr_pages - 1;
        if (idx != buf->intr_pos) {
                buf->intr_pos = idx;
                buf->intr_te = pt_topa_entry_for_page(buf, idx);
                buf->intr_te = pt_topa_prev_entry(buf, buf->intr_te);
        }

        buf->stop_te->stop = 1;
        buf->stop_te->intr = 1;
        buf->intr_te->intr = 1;

        return 0;
}

/**
 * pt_buffer_reset_offsets() - adjust buffer's write pointers from aux_head
 * @buf:        PT buffer.
 * @head:       Write pointer (aux_head) from AUX buffer.
 *
 * Find the ToPA table and entry corresponding to given @head and set buffer's
 * "current" pointers accordingly. This is done after we have obtained the
 * current aux_head position from a successful call to perf_aux_output_begin()
 * to make sure the hardware is writing to the right place.
 *
 * This function modifies buf::{cur,cur_idx,output_off} that will be programmed
 * into PT msrs when the tracing is enabled and buf::head and buf::data_size,
 * which are used to determine INT and STOP markers' locations by a subsequent
 * call to pt_buffer_reset_markers().
 */
static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head)
{
        struct topa_page *cur_tp;
        struct topa_entry *te;
        int pg;

        if (buf->snapshot)
                head &= (buf->nr_pages << PAGE_SHIFT) - 1;

        if (!buf->single) {
                pg = (head >> PAGE_SHIFT) & (buf->nr_pages - 1);
                te = pt_topa_entry_for_page(buf, pg);

                cur_tp = topa_entry_to_page(te);
                buf->cur = &cur_tp->topa;
                buf->cur_idx = te - TOPA_ENTRY(buf->cur, 0);
                buf->output_off = head & (pt_buffer_region_size(buf) - 1);
        } else {
                buf->output_off = head;
        }

        local64_set(&buf->head, head);
        local_set(&buf->data_size, 0);
}

/**
 * pt_buffer_fini_topa() - deallocate ToPA structure of a buffer
 * @buf:        PT buffer.
 */
static void pt_buffer_fini_topa(struct pt_buffer *buf)
{
        struct topa *topa, *iter;

        if (buf->single)
                return;

        list_for_each_entry_safe(topa, iter, &buf->tables, list) {
                /*
                 * right now, this is in free_aux() path only, so
                 * no need to unlink this table from the list
                 */
                topa_free(topa);
        }
}

/**
 * pt_buffer_init_topa() - initialize ToPA table for pt buffer
 * @buf:        PT buffer.
 * @cpu:        CPU on which to allocate.
 * @nr_pages:   No. of pages to allocate.
 * @gfp:        Allocation flags.
 *
 * Return:      0 on success or error code.
 */
static int pt_buffer_init_topa(struct pt_buffer *buf, int cpu,
                               unsigned long nr_pages, gfp_t gfp)
{
        struct topa *topa;
        int err;

        topa = topa_alloc(cpu, gfp);
        if (!topa)
                return -ENOMEM;

        topa_insert_table(buf, topa);

        while (buf->nr_pages < nr_pages) {
                err = topa_insert_pages(buf, cpu, gfp);
                if (err) {
                        pt_buffer_fini_topa(buf);
                        return -ENOMEM;
                }
        }

        /* link last table to the first one, unless we're double buffering */
        if (intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries)) {
                TOPA_ENTRY(buf->last, -1)->base = topa_pfn(buf->first);
                TOPA_ENTRY(buf->last, -1)->end = 1;
        }

        pt_topa_dump(buf);
        return 0;
}

static int pt_buffer_try_single(struct pt_buffer *buf, int nr_pages)
{
        struct page *p = virt_to_page(buf->data_pages[0]);
        int ret = -ENOTSUPP, order = 0;

        /*
         * We can use single range output mode
         * + in snapshot mode, where we don't need interrupts;
         * + if the hardware supports it;
         * + if the entire buffer is one contiguous allocation.
         */
        if (!buf->snapshot)
                goto out;

        if (!intel_pt_validate_hw_cap(PT_CAP_single_range_output))
                goto out;

        if (PagePrivate(p))
                order = page_private(p);

        if (1 << order != nr_pages)
                goto out;

        /*
         * Some processors cannot always support single range for more than
         * 4KB - refer errata TGL052, ADL037 and RPL017. Future processors might
         * also be affected, so for now rather than trying to keep track of
         * which ones, just disable it for all.
         */
        if (nr_pages > 1)
                goto out;

        buf->single = true;
        buf->nr_pages = nr_pages;
        ret = 0;
out:
        return ret;
}

/**
 * pt_buffer_setup_aux() - set up topa tables for a PT buffer
 * @event:      Performance event
 * @pages:      Array of pointers to buffer pages passed from perf core.
 * @nr_pages:   Number of pages in the buffer.
 * @snapshot:   If this is a snapshot/overwrite counter.
 *
 * This is a pmu::setup_aux callback that sets up ToPA tables and all the
 * bookkeeping for an AUX buffer.
 *
 * Return:      Our private PT buffer structure.
 */
static void *
pt_buffer_setup_aux(struct perf_event *event, void **pages,
                    int nr_pages, bool snapshot)
{
        struct pt_buffer *buf;
        int node, ret, cpu = event->cpu;

        if (!nr_pages)
                return NULL;

        /*
         * Only support AUX sampling in snapshot mode, where we don't
         * generate NMIs.
         */
        if (event->attr.aux_sample_size && !snapshot)
                return NULL;

        if (cpu == -1)
                cpu = raw_smp_processor_id();
        node = cpu_to_node(cpu);

        buf = kzalloc_node(sizeof(struct pt_buffer), GFP_KERNEL, node);
        if (!buf)
                return NULL;

        buf->snapshot = snapshot;
        buf->data_pages = pages;
        buf->stop_pos = -1;
        buf->intr_pos = -1;

        INIT_LIST_HEAD(&buf->tables);

        ret = pt_buffer_try_single(buf, nr_pages);
        if (!ret)
                return buf;

        ret = pt_buffer_init_topa(buf, cpu, nr_pages, GFP_KERNEL);
        if (ret) {
                kfree(buf);
                return NULL;
        }

        return buf;
}

/**
 * pt_buffer_free_aux() - perf AUX deallocation path callback
 * @data:       PT buffer.
 */
static void pt_buffer_free_aux(void *data)
{
        struct pt_buffer *buf = data;

        pt_buffer_fini_topa(buf);
        kfree(buf);
}

static int pt_addr_filters_init(struct perf_event *event)
{
        struct pt_filters *filters;
        int node = event->cpu == -1 ? -1 : cpu_to_node(event->cpu);

        if (!intel_pt_validate_hw_cap(PT_CAP_num_address_ranges))
                return 0;

        filters = kzalloc_node(sizeof(struct pt_filters), GFP_KERNEL, node);
        if (!filters)
                return -ENOMEM;

        if (event->parent)
                memcpy(filters, event->parent->hw.addr_filters,
                       sizeof(*filters));

        event->hw.addr_filters = filters;

        return 0;
}

static void pt_addr_filters_fini(struct perf_event *event)
{
        kfree(event->hw.addr_filters);
        event->hw.addr_filters = NULL;
}

#ifdef CONFIG_X86_64
/* Clamp to a canonical address greater-than-or-equal-to the address given */
static u64 clamp_to_ge_canonical_addr(u64 vaddr, u8 vaddr_bits)
{
        return __is_canonical_address(vaddr, vaddr_bits) ?
               vaddr :
               -BIT_ULL(vaddr_bits - 1);
}

/* Clamp to a canonical address less-than-or-equal-to the address given */
static u64 clamp_to_le_canonical_addr(u64 vaddr, u8 vaddr_bits)
{
        return __is_canonical_address(vaddr, vaddr_bits) ?
               vaddr :
               BIT_ULL(vaddr_bits - 1) - 1;
}
#else
#define clamp_to_ge_canonical_addr(x, y) (x)
#define clamp_to_le_canonical_addr(x, y) (x)
#endif

static int pt_event_addr_filters_validate(struct list_head *filters)
{
        struct perf_addr_filter *filter;
        int range = 0;

        list_for_each_entry(filter, filters, entry) {
                /*
                 * PT doesn't support single address triggers and
                 * 'start' filters.
                 */
                if (!filter->size ||
                    filter->action == PERF_ADDR_FILTER_ACTION_START)
                        return -EOPNOTSUPP;

                if (++range > intel_pt_validate_hw_cap(PT_CAP_num_address_ranges))
                        return -EOPNOTSUPP;
        }

        return 0;
}

static void pt_event_addr_filters_sync(struct perf_event *event)
{
        struct perf_addr_filters_head *head = perf_event_addr_filters(event);
        unsigned long msr_a, msr_b;
        struct perf_addr_filter_range *fr = event->addr_filter_ranges;
        struct pt_filters *filters = event->hw.addr_filters;
        struct perf_addr_filter *filter;
        int range = 0;

        if (!filters)
                return;

        list_for_each_entry(filter, &head->list, entry) {
                if (filter->path.dentry && !fr[range].start) {
                        msr_a = msr_b = 0;
                } else {
                        unsigned long n = fr[range].size - 1;
                        unsigned long a = fr[range].start;
                        unsigned long b;

                        if (a > ULONG_MAX - n)
                                b = ULONG_MAX;
                        else
                                b = a + n;
                        /*
                         * Apply the offset. 64-bit addresses written to the
                         * MSRs must be canonical, but the range can encompass
                         * non-canonical addresses. Since software cannot
                         * execute at non-canonical addresses, adjusting to
                         * canonical addresses does not affect the result of the
                         * address filter.
                         */
                        msr_a = clamp_to_ge_canonical_addr(a, boot_cpu_data.x86_virt_bits);
                        msr_b = clamp_to_le_canonical_addr(b, boot_cpu_data.x86_virt_bits);
                        if (msr_b < msr_a)
                                msr_a = msr_b = 0;
                }

                filters->filter[range].msr_a  = msr_a;
                filters->filter[range].msr_b  = msr_b;
                if (filter->action == PERF_ADDR_FILTER_ACTION_FILTER)
                        filters->filter[range].config = 1;
                else
                        filters->filter[range].config = 2;
                range++;
        }

        filters->nr_filters = range;
}

/**
 * intel_pt_interrupt() - PT PMI handler
 */
void intel_pt_interrupt(void)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct pt_buffer *buf;
        struct perf_event *event = pt->handle.event;

        /*
         * There may be a dangling PT bit in the interrupt status register
         * after PT has been disabled by pt_event_stop(). Make sure we don't
         * do anything (particularly, re-enable) for this event here.
         */
        if (!READ_ONCE(pt->handle_nmi))
                return;

        if (!event)
                return;

        pt_config_stop(event);

        buf = perf_get_aux(&pt->handle);
        if (!buf)
                return;

        pt_read_offset(buf);

        pt_handle_status(pt);

        pt_update_head(pt);

        perf_aux_output_end(&pt->handle, local_xchg(&buf->data_size, 0));

        if (!event->hw.state) {
                int ret;

                buf = perf_aux_output_begin(&pt->handle, event);
                if (!buf) {
                        event->hw.state = PERF_HES_STOPPED;
                        return;
                }

                pt_buffer_reset_offsets(buf, pt->handle.head);
                /* snapshot counters don't use PMI, so it's safe */
                ret = pt_buffer_reset_markers(buf, &pt->handle);
                if (ret) {
                        perf_aux_output_end(&pt->handle, 0);
                        return;
                }

                pt_config_buffer(buf);
                pt_config_start(event);
        }
}

void intel_pt_handle_vmx(int on)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct perf_event *event;
        unsigned long flags;

        /* PT plays nice with VMX, do nothing */
        if (pt_pmu.vmx)
                return;

        /*
         * VMXON will clear RTIT_CTL.TraceEn; we need to make
         * sure to not try to set it while VMX is on. Disable
         * interrupts to avoid racing with pmu callbacks;
         * concurrent PMI should be handled fine.
         */
        local_irq_save(flags);
        WRITE_ONCE(pt->vmx_on, on);

        /*
         * If an AUX transaction is in progress, it will contain
         * gap(s), so flag it PARTIAL to inform the user.
         */
        event = pt->handle.event;
        if (event)
                perf_aux_output_flag(&pt->handle,
                                     PERF_AUX_FLAG_PARTIAL);

        /* Turn PTs back on */
        if (!on && event)
                wrmsrl(MSR_IA32_RTIT_CTL, event->hw.aux_config);

        local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(intel_pt_handle_vmx);

/*
 * PMU callbacks
 */

static void pt_event_start(struct perf_event *event, int mode)
{
        struct hw_perf_event *hwc = &event->hw;
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct pt_buffer *buf;

        buf = perf_aux_output_begin(&pt->handle, event);
        if (!buf)
                goto fail_stop;

        pt_buffer_reset_offsets(buf, pt->handle.head);
        if (!buf->snapshot) {
                if (pt_buffer_reset_markers(buf, &pt->handle))
                        goto fail_end_stop;
        }

        WRITE_ONCE(pt->handle_nmi, 1);
        hwc->state = 0;

        pt_config_buffer(buf);
        pt_config(event);

        return;

fail_end_stop:
        perf_aux_output_end(&pt->handle, 0);
fail_stop:
        hwc->state = PERF_HES_STOPPED;
}

static void pt_event_stop(struct perf_event *event, int mode)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);

        /*
         * Protect against the PMI racing with disabling wrmsr,
         * see comment in intel_pt_interrupt().
         */
        WRITE_ONCE(pt->handle_nmi, 0);
        barrier();

        pt_config_stop(event);

        if (event->hw.state == PERF_HES_STOPPED)
                return;

        event->hw.state = PERF_HES_STOPPED;

        if (mode & PERF_EF_UPDATE) {
                struct pt_buffer *buf = perf_get_aux(&pt->handle);

                if (!buf)
                        return;

                if (WARN_ON_ONCE(pt->handle.event != event))
                        return;

                pt_read_offset(buf);

                pt_handle_status(pt);

                pt_update_head(pt);

                if (buf->snapshot)
                        pt->handle.head =
                                local_xchg(&buf->data_size,
                                           buf->nr_pages << PAGE_SHIFT);
                perf_aux_output_end(&pt->handle, local_xchg(&buf->data_size, 0));
        }
}

static long pt_event_snapshot_aux(struct perf_event *event,
                                  struct perf_output_handle *handle,
                                  unsigned long size)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct pt_buffer *buf = perf_get_aux(&pt->handle);
        unsigned long from = 0, to;
        long ret;

        if (WARN_ON_ONCE(!buf))
                return 0;

        /*
         * Sampling is only allowed on snapshot events;
         * see pt_buffer_setup_aux().
         */
        if (WARN_ON_ONCE(!buf->snapshot))
                return 0;

        /*
         * There is no PT interrupt in this mode, so stop the trace and it will
         * remain stopped while the buffer is copied.
         */
        pt_config_stop(event);
        pt_read_offset(buf);
        pt_update_head(pt);

        to = local_read(&buf->data_size);
        if (to < size)
                from = buf->nr_pages << PAGE_SHIFT;
        from += to - size;

        ret = perf_output_copy_aux(&pt->handle, handle, from, to);

        /*
         * Here, handle_nmi tells us if the tracing was on.
         * If the tracing was on, restart it.
         */
        if (READ_ONCE(pt->handle_nmi))
                pt_config_start(event);

        return ret;
}

static void pt_event_del(struct perf_event *event, int mode)
{
        pt_event_stop(event, PERF_EF_UPDATE);
}

static int pt_event_add(struct perf_event *event, int mode)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);
        struct hw_perf_event *hwc = &event->hw;
        int ret = -EBUSY;

        if (pt->handle.event)
                goto fail;

        if (mode & PERF_EF_START) {
                pt_event_start(event, 0);
                ret = -EINVAL;
                if (hwc->state == PERF_HES_STOPPED)
                        goto fail;
        } else {
                hwc->state = PERF_HES_STOPPED;
        }

        ret = 0;
fail:

        return ret;
}

static void pt_event_read(struct perf_event *event)
{
}

static void pt_event_destroy(struct perf_event *event)
{
        pt_addr_filters_fini(event);
        x86_del_exclusive(x86_lbr_exclusive_pt);
}

static int pt_event_init(struct perf_event *event)
{
        if (event->attr.type != pt_pmu.pmu.type)
                return -ENOENT;

        if (!pt_event_valid(event))
                return -EINVAL;

        if (x86_add_exclusive(x86_lbr_exclusive_pt))
                return -EBUSY;

        if (pt_addr_filters_init(event)) {
                x86_del_exclusive(x86_lbr_exclusive_pt);
                return -ENOMEM;
        }

        event->destroy = pt_event_destroy;

        return 0;
}

void cpu_emergency_stop_pt(void)
{
        struct pt *pt = this_cpu_ptr(&pt_ctx);

        if (pt->handle.event)
                pt_event_stop(pt->handle.event, PERF_EF_UPDATE);
}

int is_intel_pt_event(struct perf_event *event)
{
        return event->pmu == &pt_pmu.pmu;
}

static __init int pt_init(void)
{
        int ret, cpu, prior_warn = 0;

        BUILD_BUG_ON(sizeof(struct topa) > PAGE_SIZE);

        if (!boot_cpu_has(X86_FEATURE_INTEL_PT))
                return -ENODEV;

        cpus_read_lock();
        for_each_online_cpu(cpu) {
                u64 ctl;

                ret = rdmsrl_safe_on_cpu(cpu, MSR_IA32_RTIT_CTL, &ctl);
                if (!ret && (ctl & RTIT_CTL_TRACEEN))
                        prior_warn++;
        }
        cpus_read_unlock();

        if (prior_warn) {
                x86_add_exclusive(x86_lbr_exclusive_pt);
                pr_warn("PT is enabled at boot time, doing nothing\n");

                return -EBUSY;
        }

        ret = pt_pmu_hw_init();
        if (ret)
                return ret;

        if (!intel_pt_validate_hw_cap(PT_CAP_topa_output)) {
                pr_warn("ToPA output is not supported on this CPU\n");
                return -ENODEV;
        }

        if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries))
                pt_pmu.pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG;

        pt_pmu.pmu.capabilities |= PERF_PMU_CAP_EXCLUSIVE | PERF_PMU_CAP_ITRACE;
        pt_pmu.pmu.attr_groups           = pt_attr_groups;
        pt_pmu.pmu.task_ctx_nr           = perf_sw_context;
        pt_pmu.pmu.event_init            = pt_event_init;
        pt_pmu.pmu.add                   = pt_event_add;
        pt_pmu.pmu.del                   = pt_event_del;
        pt_pmu.pmu.start                 = pt_event_start;
        pt_pmu.pmu.stop                  = pt_event_stop;
        pt_pmu.pmu.snapshot_aux          = pt_event_snapshot_aux;
        pt_pmu.pmu.read                  = pt_event_read;
        pt_pmu.pmu.setup_aux             = pt_buffer_setup_aux;
        pt_pmu.pmu.free_aux              = pt_buffer_free_aux;
        pt_pmu.pmu.addr_filters_sync     = pt_event_addr_filters_sync;
        pt_pmu.pmu.addr_filters_validate = pt_event_addr_filters_validate;
        pt_pmu.pmu.nr_addr_filters       =
                intel_pt_validate_hw_cap(PT_CAP_num_address_ranges);

        ret = perf_pmu_register(&pt_pmu.pmu, "intel_pt", -1);

        return ret;
}
arch_initcall(pt_init);