[PATCH 5/6] x86: KVM: Enable AVX-NE-CONVERT CPUID and expose it to guest

Jiaxi Chen
2022-10-19T08:55:50Z

AVX-NE-CONVERT is a new set of instructions in the latest Intel platform
Sierra Forest, which can convert low precision floating point like
BF16/FP16 to high precision floating point FP32. It can also convert
FP32 elements to BF16. This instruction allows the platform to have
improved AI capabilities and better compatibility.

The bit definition:
CPUID.(EAX=7,ECX=1):EDX[bit 5]

This patch enables this CPUID in the kernel feature bits and expose it
to guest OS.

Signed-off-by: Jiaxi Chen <jiaxi.chen@linux.intel.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kvm/cpuid.c | 3 ++-
2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index b2aa761ea110..4e0bbffedbb4 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -425,6 +425,7 @@

/* Intel-defined CPU features, CPUID level 0x00000007:1 (EDX), word 20 */
#define X86_FEATURE_AVX_VNNI_INT8 (20*32+ 4) /* Support for VPDPB[SU,UU,SS]D[,S] */
+#define X86_FEATURE_AVX_NE_CONVERT (20*32+ 5) /* AVX NE CONVERT Instructions */

/*
* BUG word(s)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b1b53a5c788a..fcd00c68e546 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -661,7 +661,8 @@ void kvm_set_cpu_caps(void)
F(AVX_IFMA));

kvm_cpu_cap_mask(CPUID_7_1_EDX,
- F(AVX_VNNI_INT8));
+ F(AVX_VNNI_INT8) | F(AVX_NE_CONVERT)
+ );

kvm_cpu_cap_mask(CPUID_D_1_EAX,
F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | F(XSAVES) | f_xfd
--
2.27.0