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Merge tag 'x86-cpu-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 cpu update from Ingo Molnar:
 "Add user-space CPUID faulting support for AMD CPUs"

* tag 'x86-cpu-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/CPU/AMD: Add CPUID faulting support
This commit is contained in:
Linus Torvalds
2025-07-29 19:22:21 -07:00
parent 1645f6ab96 5bf2f5119b
commit 4dd39ddeb6
4 changed files with 21 additions and 7 deletions
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3
arch/x86/include/asm/cpufeatures.h
View File

@@ -458,9 +458,12 @@
#define X86_FEATURE_LFENCE_RDTSC (20*32+ 2) /* LFENCE always serializing / synchronizes RDTSC */
#define X86_FEATURE_VERW_CLEAR (20*32+ 5) /* The memory form of VERW mitigates TSA */
#define X86_FEATURE_NULL_SEL_CLR_BASE (20*32+ 6) /* Null Selector Clears Base */
#define X86_FEATURE_AUTOIBRS (20*32+ 8) /* Automatic IBRS */
#define X86_FEATURE_NO_SMM_CTL_MSR (20*32+ 9) /* SMM_CTL MSR is not present */
#define X86_FEATURE_GP_ON_USER_CPUID (20*32+17) /* User CPUID faulting */
#define X86_FEATURE_PREFETCHI (20*32+20) /* Prefetch Data/Instruction to Cache Level */
#define X86_FEATURE_SBPB (20*32+27) /* Selective Branch Prediction Barrier */
#define X86_FEATURE_IBPB_BRTYPE (20*32+28) /* MSR_PRED_CMD[IBPB] flushes all branch type predictions */

1
arch/x86/include/asm/msr-index.h
View File

@@ -831,6 +831,7 @@
#define MSR_K7_HWCR_SMMLOCK BIT_ULL(MSR_K7_HWCR_SMMLOCK_BIT)
#define MSR_K7_HWCR_IRPERF_EN_BIT 30
#define MSR_K7_HWCR_IRPERF_EN BIT_ULL(MSR_K7_HWCR_IRPERF_EN_BIT)
#define MSR_K7_HWCR_CPUID_USER_DIS_BIT 35
#define MSR_K7_FID_VID_CTL 0xc0010041
#define MSR_K7_FID_VID_STATUS 0xc0010042
#define MSR_K7_HWCR_CPB_DIS_BIT 25

4
arch/x86/kernel/cpu/amd.c
View File

@@ -530,9 +530,11 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
}
bsp_determine_snp(c);
tsa_init(c);
if (cpu_has(c, X86_FEATURE_GP_ON_USER_CPUID))
setup_force_cpu_cap(X86_FEATURE_CPUID_FAULT);
return;
warn:

20
arch/x86/kernel/process.c
View File

@@ -334,13 +334,21 @@ DEFINE_PER_CPU(u64, msr_misc_features_shadow);
static void set_cpuid_faulting(bool on)
{
u64 msrval;
msrval = this_cpu_read(msr_misc_features_shadow);
msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT);
this_cpu_write(msr_misc_features_shadow, msrval);
wrmsrq(MSR_MISC_FEATURES_ENABLES, msrval);
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
u64 msrval;
msrval = this_cpu_read(msr_misc_features_shadow);
msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT);
this_cpu_write(msr_misc_features_shadow, msrval);
wrmsrq(MSR_MISC_FEATURES_ENABLES, msrval);
} else if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
if (on)
msr_set_bit(MSR_K7_HWCR, MSR_K7_HWCR_CPUID_USER_DIS_BIT);
else
msr_clear_bit(MSR_K7_HWCR, MSR_K7_HWCR_CPUID_USER_DIS_BIT);
}
}
static void disable_cpuid(void)