Merge tag 'sched-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel...

[linux/fpc-iii.git] / arch / x86 / xen / setup.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Machine specific setup for xen
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/pm.h>
#include <linux/memblock.h>
#include <linux/cpuidle.h>
#include <linux/cpufreq.h>
#include <linux/memory_hotplug.h>

#include <asm/elf.h>
#include <asm/vdso.h>
#include <asm/e820/api.h>
#include <asm/setup.h>
#include <asm/acpi.h>
#include <asm/numa.h>
#include <asm/idtentry.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

#include <xen/xen.h>
#include <xen/page.h>
#include <xen/interface/callback.h>
#include <xen/interface/memory.h>
#include <xen/interface/physdev.h>
#include <xen/features.h>
#include <xen/hvc-console.h>
#include "xen-ops.h"
#include "mmu.h"

#define GB(x) ((uint64_t)(x) * 1024 * 1024 * 1024)

/* Amount of extra memory space we add to the e820 ranges */
struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;

/* Number of pages released from the initial allocation. */
unsigned long xen_released_pages;

/* E820 map used during setting up memory. */
static struct e820_table xen_e820_table __initdata;

/*
 * Buffer used to remap identity mapped pages. We only need the virtual space.
 * The physical page behind this address is remapped as needed to different
 * buffer pages.
 */
#define REMAP_SIZE      (P2M_PER_PAGE - 3)
static struct {
        unsigned long   next_area_mfn;
        unsigned long   target_pfn;
        unsigned long   size;
        unsigned long   mfns[REMAP_SIZE];
} xen_remap_buf __initdata __aligned(PAGE_SIZE);
static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;

/* 
 * The maximum amount of extra memory compared to the base size.  The
 * main scaling factor is the size of struct page.  At extreme ratios
 * of base:extra, all the base memory can be filled with page
 * structures for the extra memory, leaving no space for anything
 * else.
 * 
 * 10x seems like a reasonable balance between scaling flexibility and
 * leaving a practically usable system.
 */
#define EXTRA_MEM_RATIO         (10)

static bool xen_512gb_limit __initdata = IS_ENABLED(CONFIG_XEN_512GB);

static void __init xen_parse_512gb(void)
{
        bool val = false;
        char *arg;

        arg = strstr(xen_start_info->cmd_line, "xen_512gb_limit");
        if (!arg)
                return;

        arg = strstr(xen_start_info->cmd_line, "xen_512gb_limit=");
        if (!arg)
                val = true;
        else if (strtobool(arg + strlen("xen_512gb_limit="), &val))
                return;

        xen_512gb_limit = val;
}

static void __init xen_add_extra_mem(unsigned long start_pfn,
                                     unsigned long n_pfns)
{
        int i;

        /*
         * No need to check for zero size, should happen rarely and will only
         * write a new entry regarded to be unused due to zero size.
         */
        for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
                /* Add new region. */
                if (xen_extra_mem[i].n_pfns == 0) {
                        xen_extra_mem[i].start_pfn = start_pfn;
                        xen_extra_mem[i].n_pfns = n_pfns;
                        break;
                }
                /* Append to existing region. */
                if (xen_extra_mem[i].start_pfn + xen_extra_mem[i].n_pfns ==
                    start_pfn) {
                        xen_extra_mem[i].n_pfns += n_pfns;
                        break;
                }
        }
        if (i == XEN_EXTRA_MEM_MAX_REGIONS)
                printk(KERN_WARNING "Warning: not enough extra memory regions\n");

        memblock_reserve(PFN_PHYS(start_pfn), PFN_PHYS(n_pfns));
}

static void __init xen_del_extra_mem(unsigned long start_pfn,
                                     unsigned long n_pfns)
{
        int i;
        unsigned long start_r, size_r;

        for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
                start_r = xen_extra_mem[i].start_pfn;
                size_r = xen_extra_mem[i].n_pfns;

                /* Start of region. */
                if (start_r == start_pfn) {
                        BUG_ON(n_pfns > size_r);
                        xen_extra_mem[i].start_pfn += n_pfns;
                        xen_extra_mem[i].n_pfns -= n_pfns;
                        break;
                }
                /* End of region. */
                if (start_r + size_r == start_pfn + n_pfns) {
                        BUG_ON(n_pfns > size_r);
                        xen_extra_mem[i].n_pfns -= n_pfns;
                        break;
                }
                /* Mid of region. */
                if (start_pfn > start_r && start_pfn < start_r + size_r) {
                        BUG_ON(start_pfn + n_pfns > start_r + size_r);
                        xen_extra_mem[i].n_pfns = start_pfn - start_r;
                        /* Calling memblock_reserve() again is okay. */
                        xen_add_extra_mem(start_pfn + n_pfns, start_r + size_r -
                                          (start_pfn + n_pfns));
                        break;
                }
        }
        memblock_free(PFN_PHYS(start_pfn), PFN_PHYS(n_pfns));
}

/*
 * Called during boot before the p2m list can take entries beyond the
 * hypervisor supplied p2m list. Entries in extra mem are to be regarded as
 * invalid.
 */
unsigned long __ref xen_chk_extra_mem(unsigned long pfn)
{
        int i;

        for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
                if (pfn >= xen_extra_mem[i].start_pfn &&
                    pfn < xen_extra_mem[i].start_pfn + xen_extra_mem[i].n_pfns)
                        return INVALID_P2M_ENTRY;
        }

        return IDENTITY_FRAME(pfn);
}

/*
 * Mark all pfns of extra mem as invalid in p2m list.
 */
void __init xen_inv_extra_mem(void)
{
        unsigned long pfn, pfn_s, pfn_e;
        int i;

        for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
                if (!xen_extra_mem[i].n_pfns)
                        continue;
                pfn_s = xen_extra_mem[i].start_pfn;
                pfn_e = pfn_s + xen_extra_mem[i].n_pfns;
                for (pfn = pfn_s; pfn < pfn_e; pfn++)
                        set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
        }
}

/*
 * Finds the next RAM pfn available in the E820 map after min_pfn.
 * This function updates min_pfn with the pfn found and returns
 * the size of that range or zero if not found.
 */
static unsigned long __init xen_find_pfn_range(unsigned long *min_pfn)
{
        const struct e820_entry *entry = xen_e820_table.entries;
        unsigned int i;
        unsigned long done = 0;

        for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
                unsigned long s_pfn;
                unsigned long e_pfn;

                if (entry->type != E820_TYPE_RAM)
                        continue;

                e_pfn = PFN_DOWN(entry->addr + entry->size);

                /* We only care about E820 after this */
                if (e_pfn <= *min_pfn)
                        continue;

                s_pfn = PFN_UP(entry->addr);

                /* If min_pfn falls within the E820 entry, we want to start
                 * at the min_pfn PFN.
                 */
                if (s_pfn <= *min_pfn) {
                        done = e_pfn - *min_pfn;
                } else {
                        done = e_pfn - s_pfn;
                        *min_pfn = s_pfn;
                }
                break;
        }

        return done;
}

static int __init xen_free_mfn(unsigned long mfn)
{
        struct xen_memory_reservation reservation = {
                .address_bits = 0,
                .extent_order = 0,
                .domid        = DOMID_SELF
        };

        set_xen_guest_handle(reservation.extent_start, &mfn);
        reservation.nr_extents = 1;

        return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
}

/*
 * This releases a chunk of memory and then does the identity map. It's used
 * as a fallback if the remapping fails.
 */
static void __init xen_set_identity_and_release_chunk(unsigned long start_pfn,
                        unsigned long end_pfn, unsigned long nr_pages)
{
        unsigned long pfn, end;
        int ret;

        WARN_ON(start_pfn > end_pfn);

        /* Release pages first. */
        end = min(end_pfn, nr_pages);
        for (pfn = start_pfn; pfn < end; pfn++) {
                unsigned long mfn = pfn_to_mfn(pfn);

                /* Make sure pfn exists to start with */
                if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
                        continue;

                ret = xen_free_mfn(mfn);
                WARN(ret != 1, "Failed to release pfn %lx err=%d\n", pfn, ret);

                if (ret == 1) {
                        xen_released_pages++;
                        if (!__set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
                                break;
                } else
                        break;
        }

        set_phys_range_identity(start_pfn, end_pfn);
}

/*
 * Helper function to update the p2m and m2p tables and kernel mapping.
 */
static void __init xen_update_mem_tables(unsigned long pfn, unsigned long mfn)
{
        struct mmu_update update = {
                .ptr = ((uint64_t)mfn << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE,
                .val = pfn
        };

        /* Update p2m */
        if (!set_phys_to_machine(pfn, mfn)) {
                WARN(1, "Failed to set p2m mapping for pfn=%ld mfn=%ld\n",
                     pfn, mfn);
                BUG();
        }

        /* Update m2p */
        if (HYPERVISOR_mmu_update(&update, 1, NULL, DOMID_SELF) < 0) {
                WARN(1, "Failed to set m2p mapping for mfn=%ld pfn=%ld\n",
                     mfn, pfn);
                BUG();
        }

        /* Update kernel mapping, but not for highmem. */
        if (pfn >= PFN_UP(__pa(high_memory - 1)))
                return;

        if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
                                         mfn_pte(mfn, PAGE_KERNEL), 0)) {
                WARN(1, "Failed to update kernel mapping for mfn=%ld pfn=%ld\n",
                      mfn, pfn);
                BUG();
        }
}

/*
 * This function updates the p2m and m2p tables with an identity map from
 * start_pfn to start_pfn+size and prepares remapping the underlying RAM of the
 * original allocation at remap_pfn. The information needed for remapping is
 * saved in the memory itself to avoid the need for allocating buffers. The
 * complete remap information is contained in a list of MFNs each containing
 * up to REMAP_SIZE MFNs and the start target PFN for doing the remap.
 * This enables us to preserve the original mfn sequence while doing the
 * remapping at a time when the memory management is capable of allocating
 * virtual and physical memory in arbitrary amounts, see 'xen_remap_memory' and
 * its callers.
 */
static void __init xen_do_set_identity_and_remap_chunk(
        unsigned long start_pfn, unsigned long size, unsigned long remap_pfn)
{
        unsigned long buf = (unsigned long)&xen_remap_buf;
        unsigned long mfn_save, mfn;
        unsigned long ident_pfn_iter, remap_pfn_iter;
        unsigned long ident_end_pfn = start_pfn + size;
        unsigned long left = size;
        unsigned int i, chunk;

        WARN_ON(size == 0);

        mfn_save = virt_to_mfn(buf);

        for (ident_pfn_iter = start_pfn, remap_pfn_iter = remap_pfn;
             ident_pfn_iter < ident_end_pfn;
             ident_pfn_iter += REMAP_SIZE, remap_pfn_iter += REMAP_SIZE) {
                chunk = (left < REMAP_SIZE) ? left : REMAP_SIZE;

                /* Map first pfn to xen_remap_buf */
                mfn = pfn_to_mfn(ident_pfn_iter);
                set_pte_mfn(buf, mfn, PAGE_KERNEL);

                /* Save mapping information in page */
                xen_remap_buf.next_area_mfn = xen_remap_mfn;
                xen_remap_buf.target_pfn = remap_pfn_iter;
                xen_remap_buf.size = chunk;
                for (i = 0; i < chunk; i++)
                        xen_remap_buf.mfns[i] = pfn_to_mfn(ident_pfn_iter + i);

                /* Put remap buf into list. */
                xen_remap_mfn = mfn;

                /* Set identity map */
                set_phys_range_identity(ident_pfn_iter, ident_pfn_iter + chunk);

                left -= chunk;
        }

        /* Restore old xen_remap_buf mapping */
        set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
}

/*
 * This function takes a contiguous pfn range that needs to be identity mapped
 * and:
 *
 *  1) Finds a new range of pfns to use to remap based on E820 and remap_pfn.
 *  2) Calls the do_ function to actually do the mapping/remapping work.
 *
 * The goal is to not allocate additional memory but to remap the existing
 * pages. In the case of an error the underlying memory is simply released back
 * to Xen and not remapped.
 */
static unsigned long __init xen_set_identity_and_remap_chunk(
        unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
        unsigned long remap_pfn)
{
        unsigned long pfn;
        unsigned long i = 0;
        unsigned long n = end_pfn - start_pfn;

        if (remap_pfn == 0)
                remap_pfn = nr_pages;

        while (i < n) {
                unsigned long cur_pfn = start_pfn + i;
                unsigned long left = n - i;
                unsigned long size = left;
                unsigned long remap_range_size;

                /* Do not remap pages beyond the current allocation */
                if (cur_pfn >= nr_pages) {
                        /* Identity map remaining pages */
                        set_phys_range_identity(cur_pfn, cur_pfn + size);
                        break;
                }
                if (cur_pfn + size > nr_pages)
                        size = nr_pages - cur_pfn;

                remap_range_size = xen_find_pfn_range(&remap_pfn);
                if (!remap_range_size) {
                        pr_warn("Unable to find available pfn range, not remapping identity pages\n");
                        xen_set_identity_and_release_chunk(cur_pfn,
                                                cur_pfn + left, nr_pages);
                        break;
                }
                /* Adjust size to fit in current e820 RAM region */
                if (size > remap_range_size)
                        size = remap_range_size;

                xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn);

                /* Update variables to reflect new mappings. */
                i += size;
                remap_pfn += size;
        }

        /*
         * If the PFNs are currently mapped, the VA mapping also needs
         * to be updated to be 1:1.
         */
        for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++)
                (void)HYPERVISOR_update_va_mapping(
                        (unsigned long)__va(pfn << PAGE_SHIFT),
                        mfn_pte(pfn, PAGE_KERNEL_IO), 0);

        return remap_pfn;
}

static unsigned long __init xen_count_remap_pages(
        unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
        unsigned long remap_pages)
{
        if (start_pfn >= nr_pages)
                return remap_pages;

        return remap_pages + min(end_pfn, nr_pages) - start_pfn;
}

static unsigned long __init xen_foreach_remap_area(unsigned long nr_pages,
        unsigned long (*func)(unsigned long start_pfn, unsigned long end_pfn,
                              unsigned long nr_pages, unsigned long last_val))
{
        phys_addr_t start = 0;
        unsigned long ret_val = 0;
        const struct e820_entry *entry = xen_e820_table.entries;
        int i;

        /*
         * Combine non-RAM regions and gaps until a RAM region (or the
         * end of the map) is reached, then call the provided function
         * to perform its duty on the non-RAM region.
         *
         * The combined non-RAM regions are rounded to a whole number
         * of pages so any partial pages are accessible via the 1:1
         * mapping.  This is needed for some BIOSes that put (for
         * example) the DMI tables in a reserved region that begins on
         * a non-page boundary.
         */
        for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
                phys_addr_t end = entry->addr + entry->size;
                if (entry->type == E820_TYPE_RAM || i == xen_e820_table.nr_entries - 1) {
                        unsigned long start_pfn = PFN_DOWN(start);
                        unsigned long end_pfn = PFN_UP(end);

                        if (entry->type == E820_TYPE_RAM)
                                end_pfn = PFN_UP(entry->addr);

                        if (start_pfn < end_pfn)
                                ret_val = func(start_pfn, end_pfn, nr_pages,
                                               ret_val);
                        start = end;
                }
        }

        return ret_val;
}

/*
 * Remap the memory prepared in xen_do_set_identity_and_remap_chunk().
 * The remap information (which mfn remap to which pfn) is contained in the
 * to be remapped memory itself in a linked list anchored at xen_remap_mfn.
 * This scheme allows to remap the different chunks in arbitrary order while
 * the resulting mapping will be independent from the order.
 */
void __init xen_remap_memory(void)
{
        unsigned long buf = (unsigned long)&xen_remap_buf;
        unsigned long mfn_save, pfn;
        unsigned long remapped = 0;
        unsigned int i;
        unsigned long pfn_s = ~0UL;
        unsigned long len = 0;

        mfn_save = virt_to_mfn(buf);

        while (xen_remap_mfn != INVALID_P2M_ENTRY) {
                /* Map the remap information */
                set_pte_mfn(buf, xen_remap_mfn, PAGE_KERNEL);

                BUG_ON(xen_remap_mfn != xen_remap_buf.mfns[0]);

                pfn = xen_remap_buf.target_pfn;
                for (i = 0; i < xen_remap_buf.size; i++) {
                        xen_update_mem_tables(pfn, xen_remap_buf.mfns[i]);
                        remapped++;
                        pfn++;
                }
                if (pfn_s == ~0UL || pfn == pfn_s) {
                        pfn_s = xen_remap_buf.target_pfn;
                        len += xen_remap_buf.size;
                } else if (pfn_s + len == xen_remap_buf.target_pfn) {
                        len += xen_remap_buf.size;
                } else {
                        xen_del_extra_mem(pfn_s, len);
                        pfn_s = xen_remap_buf.target_pfn;
                        len = xen_remap_buf.size;
                }
                xen_remap_mfn = xen_remap_buf.next_area_mfn;
        }

        if (pfn_s != ~0UL && len)
                xen_del_extra_mem(pfn_s, len);

        set_pte_mfn(buf, mfn_save, PAGE_KERNEL);

        pr_info("Remapped %ld page(s)\n", remapped);
}

static unsigned long __init xen_get_pages_limit(void)
{
        unsigned long limit;

        limit = MAXMEM / PAGE_SIZE;
        if (!xen_initial_domain() && xen_512gb_limit)
                limit = GB(512) / PAGE_SIZE;

        return limit;
}

static unsigned long __init xen_get_max_pages(void)
{
        unsigned long max_pages, limit;
        domid_t domid = DOMID_SELF;
        long ret;

        limit = xen_get_pages_limit();
        max_pages = limit;

        /*
         * For the initial domain we use the maximum reservation as
         * the maximum page.
         *
         * For guest domains the current maximum reservation reflects
         * the current maximum rather than the static maximum. In this
         * case the e820 map provided to us will cover the static
         * maximum region.
         */
        if (xen_initial_domain()) {
                ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
                if (ret > 0)
                        max_pages = ret;
        }

        return min(max_pages, limit);
}

static void __init xen_align_and_add_e820_region(phys_addr_t start,
                                                 phys_addr_t size, int type)
{
        phys_addr_t end = start + size;

        /* Align RAM regions to page boundaries. */
        if (type == E820_TYPE_RAM) {
                start = PAGE_ALIGN(start);
                end &= ~((phys_addr_t)PAGE_SIZE - 1);
#ifdef CONFIG_MEMORY_HOTPLUG
                /*
                 * Don't allow adding memory not in E820 map while booting the
                 * system. Once the balloon driver is up it will remove that
                 * restriction again.
                 */
                max_mem_size = end;
#endif
        }

        e820__range_add(start, end - start, type);
}

static void __init xen_ignore_unusable(void)
{
        struct e820_entry *entry = xen_e820_table.entries;
        unsigned int i;

        for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
                if (entry->type == E820_TYPE_UNUSABLE)
                        entry->type = E820_TYPE_RAM;
        }
}

bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
{
        struct e820_entry *entry;
        unsigned mapcnt;
        phys_addr_t end;

        if (!size)
                return false;

        end = start + size;
        entry = xen_e820_table.entries;

        for (mapcnt = 0; mapcnt < xen_e820_table.nr_entries; mapcnt++) {
                if (entry->type == E820_TYPE_RAM && entry->addr <= start &&
                    (entry->addr + entry->size) >= end)
                        return false;

                entry++;
        }

        return true;
}

/*
 * Find a free area in physical memory not yet reserved and compliant with
 * E820 map.
 * Used to relocate pre-allocated areas like initrd or p2m list which are in
 * conflict with the to be used E820 map.
 * In case no area is found, return 0. Otherwise return the physical address
 * of the area which is already reserved for convenience.
 */
phys_addr_t __init xen_find_free_area(phys_addr_t size)
{
        unsigned mapcnt;
        phys_addr_t addr, start;
        struct e820_entry *entry = xen_e820_table.entries;

        for (mapcnt = 0; mapcnt < xen_e820_table.nr_entries; mapcnt++, entry++) {
                if (entry->type != E820_TYPE_RAM || entry->size < size)
                        continue;
                start = entry->addr;
                for (addr = start; addr < start + size; addr += PAGE_SIZE) {
                        if (!memblock_is_reserved(addr))
                                continue;
                        start = addr + PAGE_SIZE;
                        if (start + size > entry->addr + entry->size)
                                break;
                }
                if (addr >= start + size) {
                        memblock_reserve(start, size);
                        return start;
                }
        }

        return 0;
}

/*
 * Like memcpy, but with physical addresses for dest and src.
 */
static void __init xen_phys_memcpy(phys_addr_t dest, phys_addr_t src,
                                   phys_addr_t n)
{
        phys_addr_t dest_off, src_off, dest_len, src_len, len;
        void *from, *to;

        while (n) {
                dest_off = dest & ~PAGE_MASK;
                src_off = src & ~PAGE_MASK;
                dest_len = n;
                if (dest_len > (NR_FIX_BTMAPS << PAGE_SHIFT) - dest_off)
                        dest_len = (NR_FIX_BTMAPS << PAGE_SHIFT) - dest_off;
                src_len = n;
                if (src_len > (NR_FIX_BTMAPS << PAGE_SHIFT) - src_off)
                        src_len = (NR_FIX_BTMAPS << PAGE_SHIFT) - src_off;
                len = min(dest_len, src_len);
                to = early_memremap(dest - dest_off, dest_len + dest_off);
                from = early_memremap(src - src_off, src_len + src_off);
                memcpy(to, from, len);
                early_memunmap(to, dest_len + dest_off);
                early_memunmap(from, src_len + src_off);
                n -= len;
                dest += len;
                src += len;
        }
}

/*
 * Reserve Xen mfn_list.
 */
static void __init xen_reserve_xen_mfnlist(void)
{
        phys_addr_t start, size;

        if (xen_start_info->mfn_list >= __START_KERNEL_map) {
                start = __pa(xen_start_info->mfn_list);
                size = PFN_ALIGN(xen_start_info->nr_pages *
                                 sizeof(unsigned long));
        } else {
                start = PFN_PHYS(xen_start_info->first_p2m_pfn);
                size = PFN_PHYS(xen_start_info->nr_p2m_frames);
        }

        memblock_reserve(start, size);
        if (!xen_is_e820_reserved(start, size))
                return;

        xen_relocate_p2m();
        memblock_free(start, size);
}

/**
 * machine_specific_memory_setup - Hook for machine specific memory setup.
 **/
char * __init xen_memory_setup(void)
{
        unsigned long max_pfn, pfn_s, n_pfns;
        phys_addr_t mem_end, addr, size, chunk_size;
        u32 type;
        int rc;
        struct xen_memory_map memmap;
        unsigned long max_pages;
        unsigned long extra_pages = 0;
        int i;
        int op;

        xen_parse_512gb();
        max_pfn = xen_get_pages_limit();
        max_pfn = min(max_pfn, xen_start_info->nr_pages);
        mem_end = PFN_PHYS(max_pfn);

        memmap.nr_entries = ARRAY_SIZE(xen_e820_table.entries);
        set_xen_guest_handle(memmap.buffer, xen_e820_table.entries);

#if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
        xen_saved_max_mem_size = max_mem_size;
#endif

        op = xen_initial_domain() ?
                XENMEM_machine_memory_map :
                XENMEM_memory_map;
        rc = HYPERVISOR_memory_op(op, &memmap);
        if (rc == -ENOSYS) {
                BUG_ON(xen_initial_domain());
                memmap.nr_entries = 1;
                xen_e820_table.entries[0].addr = 0ULL;
                xen_e820_table.entries[0].size = mem_end;
                /* 8MB slack (to balance backend allocations). */
                xen_e820_table.entries[0].size += 8ULL << 20;
                xen_e820_table.entries[0].type = E820_TYPE_RAM;
                rc = 0;
        }
        BUG_ON(rc);
        BUG_ON(memmap.nr_entries == 0);
        xen_e820_table.nr_entries = memmap.nr_entries;

        /*
         * Xen won't allow a 1:1 mapping to be created to UNUSABLE
         * regions, so if we're using the machine memory map leave the
         * region as RAM as it is in the pseudo-physical map.
         *
         * UNUSABLE regions in domUs are not handled and will need
         * a patch in the future.
         */
        if (xen_initial_domain())
                xen_ignore_unusable();

        /* Make sure the Xen-supplied memory map is well-ordered. */
        e820__update_table(&xen_e820_table);

        max_pages = xen_get_max_pages();

        /* How many extra pages do we need due to remapping? */
        max_pages += xen_foreach_remap_area(max_pfn, xen_count_remap_pages);

        if (max_pages > max_pfn)
                extra_pages += max_pages - max_pfn;

        /*
         * Clamp the amount of extra memory to a EXTRA_MEM_RATIO
         * factor the base size.  On non-highmem systems, the base
         * size is the full initial memory allocation; on highmem it
         * is limited to the max size of lowmem, so that it doesn't
         * get completely filled.
         *
         * Make sure we have no memory above max_pages, as this area
         * isn't handled by the p2m management.
         *
         * In principle there could be a problem in lowmem systems if
         * the initial memory is also very large with respect to
         * lowmem, but we won't try to deal with that here.
         */
        extra_pages = min3(EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
                           extra_pages, max_pages - max_pfn);
        i = 0;
        addr = xen_e820_table.entries[0].addr;
        size = xen_e820_table.entries[0].size;
        while (i < xen_e820_table.nr_entries) {
                bool discard = false;

                chunk_size = size;
                type = xen_e820_table.entries[i].type;

                if (type == E820_TYPE_RAM) {
                        if (addr < mem_end) {
                                chunk_size = min(size, mem_end - addr);
                        } else if (extra_pages) {
                                chunk_size = min(size, PFN_PHYS(extra_pages));
                                pfn_s = PFN_UP(addr);
                                n_pfns = PFN_DOWN(addr + chunk_size) - pfn_s;
                                extra_pages -= n_pfns;
                                xen_add_extra_mem(pfn_s, n_pfns);
                                xen_max_p2m_pfn = pfn_s + n_pfns;
                        } else
                                discard = true;
                }

                if (!discard)
                        xen_align_and_add_e820_region(addr, chunk_size, type);

                addr += chunk_size;
                size -= chunk_size;
                if (size == 0) {
                        i++;
                        if (i < xen_e820_table.nr_entries) {
                                addr = xen_e820_table.entries[i].addr;
                                size = xen_e820_table.entries[i].size;
                        }
                }
        }

        /*
         * Set the rest as identity mapped, in case PCI BARs are
         * located here.
         */
        set_phys_range_identity(addr / PAGE_SIZE, ~0ul);

        /*
         * In domU, the ISA region is normal, usable memory, but we
         * reserve ISA memory anyway because too many things poke
         * about in there.
         */
        e820__range_add(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS, E820_TYPE_RESERVED);

        e820__update_table(e820_table);

        /*
         * Check whether the kernel itself conflicts with the target E820 map.
         * Failing now is better than running into weird problems later due
         * to relocating (and even reusing) pages with kernel text or data.
         */
        if (xen_is_e820_reserved(__pa_symbol(_text),
                        __pa_symbol(__bss_stop) - __pa_symbol(_text))) {
                xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
                BUG();
        }

        /*
         * Check for a conflict of the hypervisor supplied page tables with
         * the target E820 map.
         */
        xen_pt_check_e820();

        xen_reserve_xen_mfnlist();

        /* Check for a conflict of the initrd with the target E820 map. */
        if (xen_is_e820_reserved(boot_params.hdr.ramdisk_image,
                                 boot_params.hdr.ramdisk_size)) {
                phys_addr_t new_area, start, size;

                new_area = xen_find_free_area(boot_params.hdr.ramdisk_size);
                if (!new_area) {
                        xen_raw_console_write("Can't find new memory area for initrd needed due to E820 map conflict\n");
                        BUG();
                }

                start = boot_params.hdr.ramdisk_image;
                size = boot_params.hdr.ramdisk_size;
                xen_phys_memcpy(new_area, start, size);
                pr_info("initrd moved from [mem %#010llx-%#010llx] to [mem %#010llx-%#010llx]\n",
                        start, start + size, new_area, new_area + size);
                memblock_free(start, size);
                boot_params.hdr.ramdisk_image = new_area;
                boot_params.ext_ramdisk_image = new_area >> 32;
        }

        /*
         * Set identity map on non-RAM pages and prepare remapping the
         * underlying RAM.
         */
        xen_foreach_remap_area(max_pfn, xen_set_identity_and_remap_chunk);

        pr_info("Released %ld page(s)\n", xen_released_pages);

        return "Xen";
}

static int register_callback(unsigned type, const void *func)
{
        struct callback_register callback = {
                .type = type,
                .address = XEN_CALLBACK(__KERNEL_CS, func),
                .flags = CALLBACKF_mask_events,
        };

        return HYPERVISOR_callback_op(CALLBACKOP_register, &callback);
}

void xen_enable_sysenter(void)
{
        int ret;
        unsigned sysenter_feature;

        sysenter_feature = X86_FEATURE_SYSENTER32;

        if (!boot_cpu_has(sysenter_feature))
                return;

        ret = register_callback(CALLBACKTYPE_sysenter, xen_sysenter_target);
        if(ret != 0)
                setup_clear_cpu_cap(sysenter_feature);
}

void xen_enable_syscall(void)
{
        int ret;

        ret = register_callback(CALLBACKTYPE_syscall, xen_syscall_target);
        if (ret != 0) {
                printk(KERN_ERR "Failed to set syscall callback: %d\n", ret);
                /* Pretty fatal; 64-bit userspace has no other
                   mechanism for syscalls. */
        }

        if (boot_cpu_has(X86_FEATURE_SYSCALL32)) {
                ret = register_callback(CALLBACKTYPE_syscall32,
                                        xen_syscall32_target);
                if (ret != 0)
                        setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
        }
}

static void __init xen_pvmmu_arch_setup(void)
{
        HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);
        HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_writable_pagetables);

        HYPERVISOR_vm_assist(VMASST_CMD_enable,
                             VMASST_TYPE_pae_extended_cr3);

        if (register_callback(CALLBACKTYPE_event,
                              xen_asm_exc_xen_hypervisor_callback) ||
            register_callback(CALLBACKTYPE_failsafe, xen_failsafe_callback))
                BUG();

        xen_enable_sysenter();
        xen_enable_syscall();
}

/* This function is not called for HVM domains */
void __init xen_arch_setup(void)
{
        xen_panic_handler_init();
        xen_pvmmu_arch_setup();

#ifdef CONFIG_ACPI
        if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
                printk(KERN_INFO "ACPI in unprivileged domain disabled\n");
                disable_acpi();
        }
#endif

        memcpy(boot_command_line, xen_start_info->cmd_line,
               MAX_GUEST_CMDLINE > COMMAND_LINE_SIZE ?
               COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE);

        /* Set up idle, making sure it calls safe_halt() pvop */
        disable_cpuidle();
        disable_cpufreq();
        WARN_ON(xen_set_default_idle());
#ifdef CONFIG_NUMA
        numa_off = 1;
#endif
}