Re: [PATCH v2 38/66] KVM: x86: Introduce kvm_cpu_caps to replace runtime CPUID masking

Vitaly Kuznetsov
2020-03-03T15:51:43Z

Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Calculate the CPUID masks for KVM_GET_SUPPORTED_CPUID at load time using
> what is effectively a KVM-adjusted copy of boot_cpu_data, or more
> precisely, the x86_capability array in boot_cpu_data.
>
> In terms of KVM support, the vast majority of CPUID feature bits are
> constant, and *all* feature support is known at KVM load time. Rather
> than apply boot_cpu_data, which is effectively read-only after init,
> at runtime, copy it into a KVM-specific array and use *that* to mask
> CPUID registers.
>
> In additional to consolidating the masking, kvm_cpu_caps can be adjusted
> by SVM/VMX at load time and thus eliminate all feature bit manipulation
> in ->set_supported_cpuid().
>
> Opportunistically clean up a few warts:
>
> - Replace bare "unsigned" with "unsigned int" when a feature flag is
> captured in a local variable, e.g. f_nx.
>
> - Sort the CPUID masks by function, index and register (alphabetically
> for registers, i.e. EBX comes before ECX/EDX).
>
> - Remove the superfluous /* cpuid 7.0.ecx */ comments.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/cpuid.c | 231 +++++++++++++++++++++++--------------------
> arch/x86/kvm/cpuid.h | 19 ++++
> arch/x86/kvm/x86.c | 2 +
> 3 files changed, 144 insertions(+), 108 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index c2e70cd0dbf1..f0b6885d2415 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -24,6 +24,13 @@
> #include "trace.h"
> #include "pmu.h"
>
> +/*
> + * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be
> + * aligned to sizeof(unsigned long) because it's not accessed via bitops.
> + */
> +u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
> +EXPORT_SYMBOL_GPL(kvm_cpu_caps);
> +
> static u32 xstate_required_size(u64 xstate_bv, bool compacted)
> {
> int feature_bit = 0;
> @@ -259,7 +266,121 @@ static __always_inline void cpuid_entry_mask(struct kvm_cpuid_entry2 *entry,
> {
> u32 *reg = cpuid_entry_get_reg(entry, leaf * 32);
>
> - *reg &= boot_cpu_data.x86_capability[leaf];
> + BUILD_BUG_ON(leaf >= ARRAY_SIZE(kvm_cpu_caps));
> + *reg &= kvm_cpu_caps[leaf];
> +}
> +
> +static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
> +{
> + reverse_cpuid_check(leaf);
> + kvm_cpu_caps[leaf] &= mask;
> +}
> +
> +void kvm_set_cpu_caps(void)
> +{
> + unsigned int f_nx = is_efer_nx() ? F(NX) : 0;
> +#ifdef CONFIG_X86_64
> + unsigned int f_gbpages = F(GBPAGES);
> + unsigned int f_lm = F(LM);
> +#else
> + unsigned int f_gbpages = 0;
> + unsigned int f_lm = 0;
> +#endif
> +
> + BUILD_BUG_ON(sizeof(kvm_cpu_caps) >
> + sizeof(boot_cpu_data.x86_capability));
> +
> + memcpy(&kvm_cpu_caps, &boot_cpu_data.x86_capability,
> + sizeof(kvm_cpu_caps));
> +
> + kvm_cpu_cap_mask(CPUID_1_ECX,
> + /*
> + * NOTE: MONITOR (and MWAIT) are emulated as NOP, but *not*
> + * advertised to guests via CPUID!
> + */
> + F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
> + 0 /* DS-CPL, VMX, SMX, EST */ |
> + 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
> + F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ |
> + F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
> + F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
> + 0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
> + F(F16C) | F(RDRAND)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_1_EDX,
> + F(FPU) | F(VME) | F(DE) | F(PSE) |
> + F(TSC) | F(MSR) | F(PAE) | F(MCE) |
> + F(CX8) | F(APIC) | 0 /* Reserved */ | F(SEP) |
> + F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
> + F(PAT) | F(PSE36) | 0 /* PSN */ | F(CLFLUSH) |
> + 0 /* Reserved, DS, ACPI */ | F(MMX) |
> + F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) |
> + 0 /* HTT, TM, Reserved, PBE */
> + );
> +
> + kvm_cpu_cap_mask(CPUID_7_0_EBX,
> + F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) |
> + F(BMI2) | F(ERMS) | 0 /*INVPCID*/ | F(RTM) | 0 /*MPX*/ | F(RDSEED) |
> + F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
> + F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> + F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | 0 /*INTEL_PT*/
> + );
> +
> + kvm_cpu_cap_mask(CPUID_7_ECX,
> + F(AVX512VBMI) | F(LA57) | 0 /*PKU*/ | 0 /*OSPKE*/ | F(RDPID) |
> + F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
> + F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
> + F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/
> + );
> + /* Set LA57 based on hardware capability. */
> + if (cpuid_ecx(7) & F(LA57))
> + kvm_cpu_cap_set(X86_FEATURE_LA57);
> +
> + kvm_cpu_cap_mask(CPUID_7_EDX,
> + F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> + F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
> + F(MD_CLEAR)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_7_1_EAX,
> + F(AVX512_BF16)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_D_1_EAX,
> + F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_8000_0001_ECX,
> + F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
> + F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
> + F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) |
> + 0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM) |
> + F(TOPOEXT) | F(PERFCTR_CORE)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_8000_0001_EDX,
> + F(FPU) | F(VME) | F(DE) | F(PSE) |
> + F(TSC) | F(MSR) | F(PAE) | F(MCE) |
> + F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) |
> + F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
> + F(PAT) | F(PSE36) | 0 /* Reserved */ |
> + f_nx | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
> + F(FXSR) | F(FXSR_OPT) | f_gbpages | F(RDTSCP) |
> + 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_8000_0008_EBX,
> + F(CLZERO) | F(XSAVEERPTR) |
> + F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) |
> + F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON)
> + );
> +
> + kvm_cpu_cap_mask(CPUID_C000_0001_EDX,
> + F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
> + F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
> + F(PMM) | F(PMM_EN)
> + );
> }
>
> struct kvm_cpuid_array {
> @@ -339,48 +460,13 @@ static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func)
>
> static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
> {
> - unsigned f_la57;
> -
> - /* cpuid 7.0.ebx */
> - const u32 kvm_cpuid_7_0_ebx_x86_features =
> - F(FSGSBASE) | F(BMI1) | F(HLE) | F(AVX2) | F(SMEP) |
> - F(BMI2) | F(ERMS) | 0 /*INVPCID*/ | F(RTM) | 0 /*MPX*/ | F(RDSEED) |
> - F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
> - F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> - F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | 0 /*INTEL_PT*/;
> -
> - /* cpuid 7.0.ecx*/
> - const u32 kvm_cpuid_7_0_ecx_x86_features =
> - F(AVX512VBMI) | F(LA57) | 0 /*PKU*/ | 0 /*OSPKE*/ | F(RDPID) |
> - F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
> - F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
> - F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/;
> -
> - /* cpuid 7.0.edx*/
> - const u32 kvm_cpuid_7_0_edx_x86_features =
> - F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> - F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
> - F(MD_CLEAR);
> -
> - /* cpuid 7.1.eax */
> - const u32 kvm_cpuid_7_1_eax_x86_features =
> - F(AVX512_BF16);
> -
> switch (entry->index) {
> case 0:
> entry->eax = min(entry->eax, 1u);
> - entry->ebx &= kvm_cpuid_7_0_ebx_x86_features;
> cpuid_entry_mask(entry, CPUID_7_0_EBX);
> /* TSC_ADJUST is emulated */
> cpuid_entry_set(entry, X86_FEATURE_TSC_ADJUST);
> -
> - entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
> - f_la57 = cpuid_entry_get(entry, X86_FEATURE_LA57);
> cpuid_entry_mask(entry, CPUID_7_ECX);
> - /* Set LA57 based on hardware capability. */
> - entry->ecx |= f_la57;
> -
> - entry->edx &= kvm_cpuid_7_0_edx_x86_features;
> cpuid_entry_mask(entry, CPUID_7_EDX);
> if (boot_cpu_has(X86_FEATURE_IBPB) && boot_cpu_has(X86_FEATURE_IBRS))
> cpuid_entry_set(entry, X86_FEATURE_SPEC_CTRL);
> @@ -395,7 +481,7 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry)
> cpuid_entry_set(entry, X86_FEATURE_ARCH_CAPABILITIES);
> break;
> case 1:
> - entry->eax &= kvm_cpuid_7_1_eax_x86_features;
> + cpuid_entry_mask(entry, CPUID_7_1_EAX);
> entry->ebx = 0;
> entry->ecx = 0;
> entry->edx = 0;
> @@ -414,72 +500,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> {
> struct kvm_cpuid_entry2 *entry;
> int r, i, max_idx;
> - unsigned f_nx = is_efer_nx() ? F(NX) : 0;
> -#ifdef CONFIG_X86_64
> - unsigned f_gbpages = F(GBPAGES);
> - unsigned f_lm = F(LM);
> -#else
> - unsigned f_gbpages = 0;
> - unsigned f_lm = 0;
> -#endif
> unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;
>
> - /* cpuid 1.edx */
> - const u32 kvm_cpuid_1_edx_x86_features =
> - F(FPU) | F(VME) | F(DE) | F(PSE) |
> - F(TSC) | F(MSR) | F(PAE) | F(MCE) |
> - F(CX8) | F(APIC) | 0 /* Reserved */ | F(SEP) |
> - F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
> - F(PAT) | F(PSE36) | 0 /* PSN */ | F(CLFLUSH) |
> - 0 /* Reserved, DS, ACPI */ | F(MMX) |
> - F(FXSR) | F(XMM) | F(XMM2) | F(SELFSNOOP) |
> - 0 /* HTT, TM, Reserved, PBE */;
> - /* cpuid 0x80000001.edx */
> - const u32 kvm_cpuid_8000_0001_edx_x86_features =
> - F(FPU) | F(VME) | F(DE) | F(PSE) |
> - F(TSC) | F(MSR) | F(PAE) | F(MCE) |
> - F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) |
> - F(MTRR) | F(PGE) | F(MCA) | F(CMOV) |
> - F(PAT) | F(PSE36) | 0 /* Reserved */ |
> - f_nx | 0 /* Reserved */ | F(MMXEXT) | F(MMX) |
> - F(FXSR) | F(FXSR_OPT) | f_gbpages | F(RDTSCP) |
> - 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW);
> - /* cpuid 1.ecx */
> - const u32 kvm_cpuid_1_ecx_x86_features =
> - /* NOTE: MONITOR (and MWAIT) are emulated as NOP,
> - * but *not* advertised to guests via CPUID ! */
> - F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
> - 0 /* DS-CPL, VMX, SMX, EST */ |
> - 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
> - F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ |
> - F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
> - F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
> - 0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
> - F(F16C) | F(RDRAND);
> - /* cpuid 0x80000001.ecx */
> - const u32 kvm_cpuid_8000_0001_ecx_x86_features =
> - F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
> - F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
> - F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) |
> - 0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM) |
> - F(TOPOEXT) | F(PERFCTR_CORE);
> -
> - /* cpuid 0x80000008.ebx */
> - const u32 kvm_cpuid_8000_0008_ebx_x86_features =
> - F(CLZERO) | F(XSAVEERPTR) |
> - F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) |
> - F(AMD_SSB_NO) | F(AMD_STIBP) | F(AMD_STIBP_ALWAYS_ON);
> -
> - /* cpuid 0xC0000001.edx */
> - const u32 kvm_cpuid_C000_0001_edx_x86_features =
> - F(XSTORE) | F(XSTORE_EN) | F(XCRYPT) | F(XCRYPT_EN) |
> - F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
> - F(PMM) | F(PMM_EN);
> -
> - /* cpuid 0xD.1.eax */
> - const u32 kvm_cpuid_D_1_eax_x86_features =
> - F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES);
> -
> /* all calls to cpuid_count() should be made on the same cpu */
> get_cpu();
>
> @@ -495,9 +517,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> entry->eax = min(entry->eax, 0x1fU);
> break;
> case 1:
> - entry->edx &= kvm_cpuid_1_edx_x86_features;
> cpuid_entry_mask(entry, CPUID_1_EDX);
> - entry->ecx &= kvm_cpuid_1_ecx_x86_features;
> cpuid_entry_mask(entry, CPUID_1_ECX);
> /* we support x2apic emulation even if host does not support
> * it since we emulate x2apic in software */
> @@ -607,7 +627,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> if (!entry)
> goto out;
>
> - entry->eax &= kvm_cpuid_D_1_eax_x86_features;
> cpuid_entry_mask(entry, CPUID_D_1_EAX);
>
> if (!kvm_x86_ops->xsaves_supported())
> @@ -691,9 +710,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> entry->eax = min(entry->eax, 0x8000001f);
> break;
> case 0x80000001:
> - entry->edx &= kvm_cpuid_8000_0001_edx_x86_features;
> cpuid_entry_mask(entry, CPUID_8000_0001_EDX);
> - entry->ecx &= kvm_cpuid_8000_0001_ecx_x86_features;
> cpuid_entry_mask(entry, CPUID_8000_0001_ECX);
> break;
> case 0x80000007: /* Advanced power management */
> @@ -712,7 +729,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> g_phys_as = phys_as;
> entry->eax = g_phys_as | (virt_as << 8);
> entry->edx = 0;
> - entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features;
> cpuid_entry_mask(entry, CPUID_8000_0008_EBX);
> /*
> * AMD has separate bits for each SPEC_CTRL bit.
> @@ -755,7 +771,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> entry->eax = min(entry->eax, 0xC0000004);
> break;
> case 0xC0000001:
> - entry->edx &= kvm_cpuid_C000_0001_edx_x86_features;
> cpuid_entry_mask(entry, CPUID_C000_0001_EDX);
> break;
> case 3: /* Processor serial number */
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index de3c6c365a5a..b899ba4bc918 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -6,6 +6,9 @@
> #include <asm/cpu.h>
> #include <asm/processor.h>
>
> +extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
> +void kvm_set_cpu_caps(void);
> +
> int kvm_update_cpuid(struct kvm_vcpu *vcpu);
> struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
> u32 function, u32 index);
> @@ -254,4 +257,20 @@ static inline bool cpuid_fault_enabled(struct kvm_vcpu *vcpu)
> MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
> }
>
> +static __always_inline void kvm_cpu_cap_clear(unsigned int x86_feature)
> +{
> + unsigned int x86_leaf = x86_feature / 32;
> +
> + reverse_cpuid_check(x86_leaf);
> + kvm_cpu_caps[x86_leaf] &= ~__feature_bit(x86_feature);
> +}
> +
> +static __always_inline void kvm_cpu_cap_set(unsigned int x86_feature)
> +{
> + unsigned int x86_leaf = x86_feature / 32;
> +
> + reverse_cpuid_check(x86_leaf);
> + kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
> +}
> +
> #endif
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e3598fe171a5..b032fd144073 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9560,6 +9560,8 @@ int kvm_arch_hardware_setup(void)
> {
> int r;
>
> + kvm_set_cpu_caps();
> +
> r = kvm_x86_ops->hardware_setup();
> if (r != 0)
> return r;

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly