kvm: x86: Add CPUID support for Intel AMX

Extend CPUID emulation to support XFD, AMX_TILE, AMX_INT8 and
AMX_BF16. Adding those bits into kvm_cpu_caps finally activates all
previous logics in this series.

Hide XFD on 32bit host kernels. Otherwise it leads to a weird situation
where KVM tells userspace to migrate MSR_IA32_XFD and then rejects
attempts to read/write the MSR.

Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-17-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index d5b5f2ab87a0b76fa42ab5313146d0a622cd2162..da872b6f8d8b6afff677c99bd9bb6f6cc2217e03 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -299,7 +299,9 @@
 /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
 #define X86_FEATURE_AVX_VNNI           (12*32+ 4) /* AVX VNNI instructions */
 #define X86_FEATURE_AVX512_BF16                (12*32+ 5) /* AVX512 BFLOAT16 instructions */
+#define X86_FEATURE_AMX_BF16           (18*32+22) /* AMX bf16 Support */
 #define X86_FEATURE_AMX_TILE           (18*32+24) /* AMX tile Support */
+#define X86_FEATURE_AMX_INT8           (18*32+25) /* AMX int8 Support */
 
 /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
 #define X86_FEATURE_CLZERO             (13*32+ 0) /* CLZERO instruction */

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index a0fedf1514ab379eb5ed23eb83392def05e55c9f..ba4c3d5d2386f510a18bb9c274d55d61a3a3bcdd 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -442,9 +442,11 @@ void kvm_set_cpu_caps(void)
 #ifdef CONFIG_X86_64
        unsigned int f_gbpages = F(GBPAGES);
        unsigned int f_lm = F(LM);
+       unsigned int f_xfd = F(XFD);
 #else
        unsigned int f_gbpages = 0;
        unsigned int f_lm = 0;
+       unsigned int f_xfd = 0;
 #endif
        memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps));
 
@@ -512,7 +514,8 @@ void kvm_set_cpu_caps(void)
                F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
                F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
                F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) |
-               F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16)
+               F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) |
+               F(AMX_TILE) | F(AMX_INT8) | F(AMX_BF16)
        );
 
        /* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
@@ -531,7 +534,7 @@ void kvm_set_cpu_caps(void)
        );
 
        kvm_cpu_cap_mask(CPUID_D_1_EAX,
-               F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES)
+               F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES) | f_xfd
        );
 
        kvm_cpu_cap_init_scattered(CPUID_12_EAX,
@@ -657,6 +660,8 @@ static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array,
        case 0x14:
        case 0x17:
        case 0x18:
+       case 0x1d:
+       case 0x1e:
        case 0x1f:
        case 0x8000001d:
                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
@@ -929,6 +934,24 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                                goto out;
                }
                break;
+       /* Intel AMX TILE */
+       case 0x1d:
+               if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
+                       entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+                       break;
+               }
+
+               for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
+                       if (!do_host_cpuid(array, function, i))
+                               goto out;
+               }
+               break;
+       case 0x1e: /* TMUL information */
+               if (!kvm_cpu_cap_has(X86_FEATURE_AMX_TILE)) {
+                       entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+                       break;
+               }
+               break;
        case KVM_CPUID_SIGNATURE: {
                const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
                entry->eax = KVM_CPUID_FEATURES;