Merge branch 'akpm'

[linux-2.6/next.git] / arch / x86 / kernel / cpu / amd.c

#include <linux/export.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/elf.h>
#include <linux/mm.h>

#include <linux/io.h>
#include <asm/processor.h>
#include <asm/apic.h>
#include <asm/cpu.h>
#include <asm/pci-direct.h>

#ifdef CONFIG_X86_64
# include <asm/numa_64.h>
# include <asm/mmconfig.h>
# include <asm/cacheflush.h>
#endif

#include "cpu.h"

#ifdef CONFIG_X86_32
/*
 *      B step AMD K6 before B 9730xxxx have hardware bugs that can cause
 *      misexecution of code under Linux. Owners of such processors should
 *      contact AMD for precise details and a CPU swap.
 *
 *      See     http://www.multimania.com/poulot/k6bug.html
 *              http://www.amd.com/K6/k6docs/revgd.html
 *
 *      The following test is erm.. interesting. AMD neglected to up
 *      the chip setting when fixing the bug but they also tweaked some
 *      performance at the same time..
 */

extern void vide(void);
__asm__(".align 4\nvide: ret");

static void __cpuinit init_amd_k5(struct cpuinfo_x86 *c)
{
/*
 * General Systems BIOSen alias the cpu frequency registers
 * of the Elan at 0x000df000. Unfortuantly, one of the Linux
 * drivers subsequently pokes it, and changes the CPU speed.
 * Workaround : Remove the unneeded alias.
 */
#define CBAR            (0xfffc) /* Configuration Base Address  (32-bit) */
#define CBAR_ENB        (0x80000000)
#define CBAR_KEY        (0X000000CB)
        if (c->x86_model == 9 || c->x86_model == 10) {
                if (inl(CBAR) & CBAR_ENB)
                        outl(0 | CBAR_KEY, CBAR);
        }
}


static void __cpuinit init_amd_k6(struct cpuinfo_x86 *c)
{
        u32 l, h;
        int mbytes = num_physpages >> (20-PAGE_SHIFT);

        if (c->x86_model < 6) {
                /* Based on AMD doc 20734R - June 2000 */
                if (c->x86_model == 0) {
                        clear_cpu_cap(c, X86_FEATURE_APIC);
                        set_cpu_cap(c, X86_FEATURE_PGE);
                }
                return;
        }

        if (c->x86_model == 6 && c->x86_mask == 1) {
                const int K6_BUG_LOOP = 1000000;
                int n;
                void (*f_vide)(void);
                unsigned long d, d2;

                printk(KERN_INFO "AMD K6 stepping B detected - ");

                /*
                 * It looks like AMD fixed the 2.6.2 bug and improved indirect
                 * calls at the same time.
                 */

                n = K6_BUG_LOOP;
                f_vide = vide;
                rdtscl(d);
                while (n--)
                        f_vide();
                rdtscl(d2);
                d = d2-d;

                if (d > 20*K6_BUG_LOOP)
                        printk(KERN_CONT
                                "system stability may be impaired when more than 32 MB are used.\n");
                else
                        printk(KERN_CONT "probably OK (after B9730xxxx).\n");
                printk(KERN_INFO "Please see http://membres.lycos.fr/poulot/k6bug.html\n");
        }

        /* K6 with old style WHCR */
        if (c->x86_model < 8 ||
           (c->x86_model == 8 && c->x86_mask < 8)) {
                /* We can only write allocate on the low 508Mb */
                if (mbytes > 508)
                        mbytes = 508;

                rdmsr(MSR_K6_WHCR, l, h);
                if ((l&0x0000FFFF) == 0) {
                        unsigned long flags;
                        l = (1<<0)|((mbytes/4)<<1);
                        local_irq_save(flags);
                        wbinvd();
                        wrmsr(MSR_K6_WHCR, l, h);
                        local_irq_restore(flags);
                        printk(KERN_INFO "Enabling old style K6 write allocation for %d Mb\n",
                                mbytes);
                }
                return;
        }

        if ((c->x86_model == 8 && c->x86_mask > 7) ||
             c->x86_model == 9 || c->x86_model == 13) {
                /* The more serious chips .. */

                if (mbytes > 4092)
                        mbytes = 4092;

                rdmsr(MSR_K6_WHCR, l, h);
                if ((l&0xFFFF0000) == 0) {
                        unsigned long flags;
                        l = ((mbytes>>2)<<22)|(1<<16);
                        local_irq_save(flags);
                        wbinvd();
                        wrmsr(MSR_K6_WHCR, l, h);
                        local_irq_restore(flags);
                        printk(KERN_INFO "Enabling new style K6 write allocation for %d Mb\n",
                                mbytes);
                }

                return;
        }

        if (c->x86_model == 10) {
                /* AMD Geode LX is model 10 */
                /* placeholder for any needed mods */
                return;
        }
}

static void __cpuinit amd_k7_smp_check(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
        /* calling is from identify_secondary_cpu() ? */
        if (!c->cpu_index)
                return;

        /*
         * Certain Athlons might work (for various values of 'work') in SMP
         * but they are not certified as MP capable.
         */
        /* Athlon 660/661 is valid. */
        if ((c->x86_model == 6) && ((c->x86_mask == 0) ||
            (c->x86_mask == 1)))
                goto valid_k7;

        /* Duron 670 is valid */
        if ((c->x86_model == 7) && (c->x86_mask == 0))
                goto valid_k7;

        /*
         * Athlon 662, Duron 671, and Athlon >model 7 have capability
         * bit. It's worth noting that the A5 stepping (662) of some
         * Athlon XP's have the MP bit set.
         * See http://www.heise.de/newsticker/data/jow-18.10.01-000 for
         * more.
         */
        if (((c->x86_model == 6) && (c->x86_mask >= 2)) ||
            ((c->x86_model == 7) && (c->x86_mask >= 1)) ||
             (c->x86_model > 7))
                if (cpu_has_mp)
                        goto valid_k7;

        /* If we get here, not a certified SMP capable AMD system. */

        /*
         * Don't taint if we are running SMP kernel on a single non-MP
         * approved Athlon
         */
        WARN_ONCE(1, "WARNING: This combination of AMD"
                " processors is not suitable for SMP.\n");
        if (!test_taint(TAINT_UNSAFE_SMP))
                add_taint(TAINT_UNSAFE_SMP);

valid_k7:
        ;
#endif
}

static void __cpuinit init_amd_k7(struct cpuinfo_x86 *c)
{
        u32 l, h;

        /*
         * Bit 15 of Athlon specific MSR 15, needs to be 0
         * to enable SSE on Palomino/Morgan/Barton CPU's.
         * If the BIOS didn't enable it already, enable it here.
         */
        if (c->x86_model >= 6 && c->x86_model <= 10) {
                if (!cpu_has(c, X86_FEATURE_XMM)) {
                        printk(KERN_INFO "Enabling disabled K7/SSE Support.\n");
                        rdmsr(MSR_K7_HWCR, l, h);
                        l &= ~0x00008000;
                        wrmsr(MSR_K7_HWCR, l, h);
                        set_cpu_cap(c, X86_FEATURE_XMM);
                }
        }

        /*
         * It's been determined by AMD that Athlons since model 8 stepping 1
         * are more robust with CLK_CTL set to 200xxxxx instead of 600xxxxx
         * As per AMD technical note 27212 0.2
         */
        if ((c->x86_model == 8 && c->x86_mask >= 1) || (c->x86_model > 8)) {
                rdmsr(MSR_K7_CLK_CTL, l, h);
                if ((l & 0xfff00000) != 0x20000000) {
                        printk(KERN_INFO
                            "CPU: CLK_CTL MSR was %x. Reprogramming to %x\n",
                                        l, ((l & 0x000fffff)|0x20000000));
                        wrmsr(MSR_K7_CLK_CTL, (l & 0x000fffff)|0x20000000, h);
                }
        }

        set_cpu_cap(c, X86_FEATURE_K7);

        amd_k7_smp_check(c);
}
#endif

#ifdef CONFIG_NUMA
/*
 * To workaround broken NUMA config.  Read the comment in
 * srat_detect_node().
 */
static int __cpuinit nearby_node(int apicid)
{
        int i, node;

        for (i = apicid - 1; i >= 0; i--) {
                node = __apicid_to_node[i];
                if (node != NUMA_NO_NODE && node_online(node))
                        return node;
        }
        for (i = apicid + 1; i < MAX_LOCAL_APIC; i++) {
                node = __apicid_to_node[i];
                if (node != NUMA_NO_NODE && node_online(node))
                        return node;
        }
        return first_node(node_online_map); /* Shouldn't happen */
}
#endif

/*
 * Fixup core topology information for
 * (1) AMD multi-node processors
 *     Assumption: Number of cores in each internal node is the same.
 * (2) AMD processors supporting compute units
 */
#ifdef CONFIG_X86_HT
static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
{
        u32 nodes, cores_per_cu = 1;
        u8 node_id;
        int cpu = smp_processor_id();

        /* get information required for multi-node processors */
        if (cpu_has(c, X86_FEATURE_TOPOEXT)) {
                u32 eax, ebx, ecx, edx;

                cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
                nodes = ((ecx >> 8) & 7) + 1;
                node_id = ecx & 7;

                /* get compute unit information */
                smp_num_siblings = ((ebx >> 8) & 3) + 1;
                c->compute_unit_id = ebx & 0xff;
                cores_per_cu += ((ebx >> 8) & 3);
        } else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
                u64 value;

                rdmsrl(MSR_FAM10H_NODE_ID, value);
                nodes = ((value >> 3) & 7) + 1;
                node_id = value & 7;
        } else
                return;

        /* fixup multi-node processor information */
        if (nodes > 1) {
                u32 cores_per_node;
                u32 cus_per_node;

                set_cpu_cap(c, X86_FEATURE_AMD_DCM);
                cores_per_node = c->x86_max_cores / nodes;
                cus_per_node = cores_per_node / cores_per_cu;

                /* store NodeID, use llc_shared_map to store sibling info */
                per_cpu(cpu_llc_id, cpu) = node_id;

                /* core id has to be in the [0 .. cores_per_node - 1] range */
                c->cpu_core_id %= cores_per_node;
                c->compute_unit_id %= cus_per_node;
        }
}
#endif

/*
 * On a AMD dual core setup the lower bits of the APIC id distingush the cores.
 * Assumes number of cores is a power of two.
 */
static void __cpuinit amd_detect_cmp(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_HT
        unsigned bits;
        int cpu = smp_processor_id();

        bits = c->x86_coreid_bits;
        /* Low order bits define the core id (index of core in socket) */
        c->cpu_core_id = c->initial_apicid & ((1 << bits)-1);
        /* Convert the initial APIC ID into the socket ID */
        c->phys_proc_id = c->initial_apicid >> bits;
        /* use socket ID also for last level cache */
        per_cpu(cpu_llc_id, cpu) = c->phys_proc_id;
        amd_get_topology(c);
#endif
}

int amd_get_nb_id(int cpu)
{
        int id = 0;
#ifdef CONFIG_SMP
        id = per_cpu(cpu_llc_id, cpu);
#endif
        return id;
}
EXPORT_SYMBOL_GPL(amd_get_nb_id);

static void __cpuinit srat_detect_node(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_NUMA
        int cpu = smp_processor_id();
        int node;
        unsigned apicid = c->apicid;

        node = numa_cpu_node(cpu);
        if (node == NUMA_NO_NODE)
                node = per_cpu(cpu_llc_id, cpu);

        if (!node_online(node)) {
                /*
                 * Two possibilities here:
                 *
                 * - The CPU is missing memory and no node was created.  In
                 *   that case try picking one from a nearby CPU.
                 *
                 * - The APIC IDs differ from the HyperTransport node IDs
                 *   which the K8 northbridge parsing fills in.  Assume
                 *   they are all increased by a constant offset, but in
                 *   the same order as the HT nodeids.  If that doesn't
                 *   result in a usable node fall back to the path for the
                 *   previous case.
                 *
                 * This workaround operates directly on the mapping between
                 * APIC ID and NUMA node, assuming certain relationship
                 * between APIC ID, HT node ID and NUMA topology.  As going
                 * through CPU mapping may alter the outcome, directly
                 * access __apicid_to_node[].
                 */
                int ht_nodeid = c->initial_apicid;

                if (ht_nodeid >= 0 &&
                    __apicid_to_node[ht_nodeid] != NUMA_NO_NODE)
                        node = __apicid_to_node[ht_nodeid];
                /* Pick a nearby node */
                if (!node_online(node))
                        node = nearby_node(apicid);
        }
        numa_set_node(cpu, node);
#endif
}

static void __cpuinit early_init_amd_mc(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_HT
        unsigned bits, ecx;

        /* Multi core CPU? */
        if (c->extended_cpuid_level < 0x80000008)
                return;

        ecx = cpuid_ecx(0x80000008);

        c->x86_max_cores = (ecx & 0xff) + 1;

        /* CPU telling us the core id bits shift? */
        bits = (ecx >> 12) & 0xF;

        /* Otherwise recompute */
        if (bits == 0) {
                while ((1 << bits) < c->x86_max_cores)
                        bits++;
        }

        c->x86_coreid_bits = bits;
#endif
}

static void __cpuinit bsp_init_amd(struct cpuinfo_x86 *c)
{
        if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {

                if (c->x86 > 0x10 ||
                    (c->x86 == 0x10 && c->x86_model >= 0x2)) {
                        u64 val;

                        rdmsrl(MSR_K7_HWCR, val);
                        if (!(val & BIT(24)))
                                printk(KERN_WARNING FW_BUG "TSC doesn't count "
                                        "with P0 frequency!\n");
                }
        }

        if (c->x86 == 0x15) {
                unsigned long upperbit;
                u32 cpuid, assoc;

                cpuid    = cpuid_edx(0x80000005);
                assoc    = cpuid >> 16 & 0xff;
                upperbit = ((cpuid >> 24) << 10) / assoc;

                va_align.mask     = (upperbit - 1) & PAGE_MASK;
                va_align.flags    = ALIGN_VA_32 | ALIGN_VA_64;
        }
}

static void __cpuinit early_init_amd(struct cpuinfo_x86 *c)
{
        early_init_amd_mc(c);

        /*
         * c->x86_power is 8000_0007 edx. Bit 8 is TSC runs at constant rate
         * with P/T states and does not stop in deep C-states
         */
        if (c->x86_power & (1 << 8)) {
                set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
                set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
        }

#ifdef CONFIG_X86_64
        set_cpu_cap(c, X86_FEATURE_SYSCALL32);
#else
        /*  Set MTRR capability flag if appropriate */
        if (c->x86 == 5)
                if (c->x86_model == 13 || c->x86_model == 9 ||
                    (c->x86_model == 8 && c->x86_mask >= 8))
                        set_cpu_cap(c, X86_FEATURE_K6_MTRR);
#endif
#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_PCI)
        /* check CPU config space for extended APIC ID */
        if (cpu_has_apic && c->x86 >= 0xf) {
                unsigned int val;
                val = read_pci_config(0, 24, 0, 0x68);
                if ((val & ((1 << 17) | (1 << 18))) == ((1 << 17) | (1 << 18)))
                        set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
        }
#endif
}

static void __cpuinit init_amd(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
        unsigned long long value;

        /*
         * Disable TLB flush filter by setting HWCR.FFDIS on K8
         * bit 6 of msr C001_0015
         *
         * Errata 63 for SH-B3 steppings
         * Errata 122 for all steppings (F+ have it disabled by default)
         */
        if (c->x86 == 0xf) {
                rdmsrl(MSR_K7_HWCR, value);
                value |= 1 << 6;
                wrmsrl(MSR_K7_HWCR, value);
        }
#endif

        early_init_amd(c);

        /*
         * Bit 31 in normal CPUID used for nonstandard 3DNow ID;
         * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway
         */
        clear_cpu_cap(c, 0*32+31);

#ifdef CONFIG_X86_64
        /* On C+ stepping K8 rep microcode works well for copy/memset */
        if (c->x86 == 0xf) {
                u32 level;

                level = cpuid_eax(1);
                if ((level >= 0x0f48 && level < 0x0f50) || level >= 0x0f58)
                        set_cpu_cap(c, X86_FEATURE_REP_GOOD);

                /*
                 * Some BIOSes incorrectly force this feature, but only K8
                 * revision D (model = 0x14) and later actually support it.
                 * (AMD Erratum #110, docId: 25759).
                 */
                if (c->x86_model < 0x14 && cpu_has(c, X86_FEATURE_LAHF_LM)) {
                        u64 val;

                        clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
                        if (!rdmsrl_amd_safe(0xc001100d, &val)) {
                                val &= ~(1ULL << 32);
                                wrmsrl_amd_safe(0xc001100d, val);
                        }
                }

        }
        if (c->x86 >= 0x10)
                set_cpu_cap(c, X86_FEATURE_REP_GOOD);

        /* get apicid instead of initial apic id from cpuid */
        c->apicid = hard_smp_processor_id();
#else

        /*
         *      FIXME: We should handle the K5 here. Set up the write
         *      range and also turn on MSR 83 bits 4 and 31 (write alloc,
         *      no bus pipeline)
         */

        switch (c->x86) {
        case 4:
                init_amd_k5(c);
                break;
        case 5:
                init_amd_k6(c);
                break;
        case 6: /* An Athlon/Duron */
                init_amd_k7(c);
                break;
        }

        /* K6s reports MCEs but don't actually have all the MSRs */
        if (c->x86 < 6)
                clear_cpu_cap(c, X86_FEATURE_MCE);
#endif

        /* Enable workaround for FXSAVE leak */
        if (c->x86 >= 6)
                set_cpu_cap(c, X86_FEATURE_FXSAVE_LEAK);

        if (!c->x86_model_id[0]) {
                switch (c->x86) {
                case 0xf:
                        /* Should distinguish Models here, but this is only
                           a fallback anyways. */
                        strcpy(c->x86_model_id, "Hammer");
                        break;
                }
        }

        cpu_detect_cache_sizes(c);

        /* Multi core CPU? */
        if (c->extended_cpuid_level >= 0x80000008) {
                amd_detect_cmp(c);
                srat_detect_node(c);
        }

#ifdef CONFIG_X86_32
        detect_ht(c);
#endif

        if (c->extended_cpuid_level >= 0x80000006) {
                if (cpuid_edx(0x80000006) & 0xf000)
                        num_cache_leaves = 4;
                else
                        num_cache_leaves = 3;
        }

        if (c->x86 >= 0xf)
                set_cpu_cap(c, X86_FEATURE_K8);

        if (cpu_has_xmm2) {
                /* MFENCE stops RDTSC speculation */
                set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC);
        }

#ifdef CONFIG_X86_64
        if (c->x86 == 0x10) {
                /* do this for boot cpu */
                if (c == &boot_cpu_data)
                        check_enable_amd_mmconf_dmi();

                fam10h_check_enable_mmcfg();
        }

        if (c == &boot_cpu_data && c->x86 >= 0xf) {
                unsigned long long tseg;

                /*
                 * Split up direct mapping around the TSEG SMM area.
                 * Don't do it for gbpages because there seems very little
                 * benefit in doing so.
                 */
                if (!rdmsrl_safe(MSR_K8_TSEG_ADDR, &tseg)) {
                        printk(KERN_DEBUG "tseg: %010llx\n", tseg);
                        if ((tseg>>PMD_SHIFT) <
                                (max_low_pfn_mapped>>(PMD_SHIFT-PAGE_SHIFT)) ||
                                ((tseg>>PMD_SHIFT) <
                                (max_pfn_mapped>>(PMD_SHIFT-PAGE_SHIFT)) &&
                                (tseg>>PMD_SHIFT) >= (1ULL<<(32 - PMD_SHIFT))))
                                set_memory_4k((unsigned long)__va(tseg), 1);
                }
        }
#endif

        /*
         * Family 0x12 and above processors have APIC timer
         * running in deep C states.
         */
        if (c->x86 > 0x11)
                set_cpu_cap(c, X86_FEATURE_ARAT);

        /*
         * Disable GART TLB Walk Errors on Fam10h. We do this here
         * because this is always needed when GART is enabled, even in a
         * kernel which has no MCE support built in.
         */
        if (c->x86 == 0x10) {
                /*
                 * BIOS should disable GartTlbWlk Errors themself. If
                 * it doesn't do it here as suggested by the BKDG.
                 *
                 * Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=33012
                 */
                u64 mask;
                int err;

                err = rdmsrl_safe(MSR_AMD64_MCx_MASK(4), &mask);
                if (err == 0) {
                        mask |= (1 << 10);
                        checking_wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
                }
        }
}

#ifdef CONFIG_X86_32
static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 *c,
                                                        unsigned int size)
{
        /* AMD errata T13 (order #21922) */
        if ((c->x86 == 6)) {
                /* Duron Rev A0 */
                if (c->x86_model == 3 && c->x86_mask == 0)
                        size = 64;
                /* Tbird rev A1/A2 */
                if (c->x86_model == 4 &&
                        (c->x86_mask == 0 || c->x86_mask == 1))
                        size = 256;
        }
        return size;
}
#endif

static const struct cpu_dev __cpuinitconst amd_cpu_dev = {
        .c_vendor       = "AMD",
        .c_ident        = { "AuthenticAMD" },
#ifdef CONFIG_X86_32
        .c_models = {
                { .vendor = X86_VENDOR_AMD, .family = 4, .model_names =
                  {
                          [3] = "486 DX/2",
                          [7] = "486 DX/2-WB",
                          [8] = "486 DX/4",
                          [9] = "486 DX/4-WB",
                          [14] = "Am5x86-WT",
                          [15] = "Am5x86-WB"
                  }
                },
        },
        .c_size_cache   = amd_size_cache,
#endif
        .c_early_init   = early_init_amd,
        .c_bsp_init     = bsp_init_amd,
        .c_init         = init_amd,
        .c_x86_vendor   = X86_VENDOR_AMD,
};

cpu_dev_register(amd_cpu_dev);

/*
 * AMD errata checking
 *
 * Errata are defined as arrays of ints using the AMD_LEGACY_ERRATUM() or
 * AMD_OSVW_ERRATUM() macros. The latter is intended for newer errata that
 * have an OSVW id assigned, which it takes as first argument. Both take a
 * variable number of family-specific model-stepping ranges created by
 * AMD_MODEL_RANGE(). Each erratum also has to be declared as extern const
 * int[] in arch/x86/include/asm/processor.h.
 *
 * Example:
 *
 * const int amd_erratum_319[] =
 *      AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0x4, 0x2),
 *                         AMD_MODEL_RANGE(0x10, 0x8, 0x0, 0x8, 0x0),
 *                         AMD_MODEL_RANGE(0x10, 0x9, 0x0, 0x9, 0x0));
 */

const int amd_erratum_400[] =
        AMD_OSVW_ERRATUM(1, AMD_MODEL_RANGE(0xf, 0x41, 0x2, 0xff, 0xf),
                            AMD_MODEL_RANGE(0x10, 0x2, 0x1, 0xff, 0xf));
EXPORT_SYMBOL_GPL(amd_erratum_400);

const int amd_erratum_383[] =
        AMD_OSVW_ERRATUM(3, AMD_MODEL_RANGE(0x10, 0, 0, 0xff, 0xf));
EXPORT_SYMBOL_GPL(amd_erratum_383);

bool cpu_has_amd_erratum(const int *erratum)
{
        struct cpuinfo_x86 *cpu = __this_cpu_ptr(&cpu_info);
        int osvw_id = *erratum++;
        u32 range;
        u32 ms;

        /*
         * If called early enough that current_cpu_data hasn't been initialized
         * yet, fall back to boot_cpu_data.
         */
        if (cpu->x86 == 0)
                cpu = &boot_cpu_data;

        if (cpu->x86_vendor != X86_VENDOR_AMD)
                return false;

        if (osvw_id >= 0 && osvw_id < 65536 &&
            cpu_has(cpu, X86_FEATURE_OSVW)) {
                u64 osvw_len;

                rdmsrl(MSR_AMD64_OSVW_ID_LENGTH, osvw_len);
                if (osvw_id < osvw_len) {
                        u64 osvw_bits;

                        rdmsrl(MSR_AMD64_OSVW_STATUS + (osvw_id >> 6),
                            osvw_bits);
                        return osvw_bits & (1ULL << (osvw_id & 0x3f));
                }
        }

        /* OSVW unavailable or ID unknown, match family-model-stepping range */
        ms = (cpu->x86_model << 4) | cpu->x86_mask;
        while ((range = *erratum++))
                if ((cpu->x86 == AMD_MODEL_RANGE_FAMILY(range)) &&
                    (ms >= AMD_MODEL_RANGE_START(range)) &&
                    (ms <= AMD_MODEL_RANGE_END(range)))
                        return true;

        return false;
}

EXPORT_SYMBOL_GPL(cpu_has_amd_erratum);