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

Sean Christopherson
2020-03-02T23:58:29Z

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;
--
2.24.1