Commit 062768f4 authored by Zhao Liu's avatar Zhao Liu Committed by Sean Christopherson
Browse files

KVM: x86: Advertise AVX10_VNNI_INT CPUID to userspace 



Define and advertise AVX10_VNNI_INT CPUID to userspace when it's supported
by the host.

AVX10_VNNI_INT (0x24.0x1.ECX[bit 2]) is a discrete feature bit
introduced on Intel Diamond Rapids, which enumerates the support for
EVEX VPDP* instructions for INT8/INT16 [*].

Since this feature has no actual kernel usages, define it as a KVM-only
feature in reverse_cpuid.h.

Advertise new CPUID subleaf 0x24.0x1 with AVX10_VNNI_INT bit to
userspace for guest use. It's safe since no additional enabling work
is needed in the host kernel.

[*]: Intel Advanced Vector Extensions 10.2 Architecture Specification
     (rev 5.0).

Tested-by: default avatarXudong Hao <xudong.hao@intel.com>
Signed-off-by: default avatarZhao Liu <zhao1.liu@intel.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Link: https://patch.msgid.link/20251120050720.931449-5-zhao1.liu@intel.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 2ff8fb1e

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -777,6 +777,7 @@ enum kvm_only_cpuid_leafs { 
	CPUID_8000_0021_ECX,

	CPUID_7_1_ECX,

	CPUID_1E_1_EAX,

	CPUID_24_1_ECX,

	NR_KVM_CPU_CAPS,



	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,

arch/x86/kvm/cpuid.c

+17 −1
Original line number Diff line number Diff line
@@ -1084,6 +1084,10 @@ void kvm_set_cpu_caps(void) 
		F(AVX10_512),

	);



	kvm_cpu_cap_init(CPUID_24_1_ECX,

		F(AVX10_VNNI_INT),

	);



	kvm_cpu_cap_init(CPUID_8000_0001_ECX,

		F(LAHF_LM),

		F(CMP_LEGACY),
@@ -1661,6 +1665,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) 
			break;

		}



		max_idx = entry->eax = min(entry->eax, 1u);

		/*

		 * The AVX10 version is encoded in EBX[7:0].  Note, the version

		 * is guaranteed to be >=1 if AVX10 is supported.  Note #2, the
@@ -1670,9 +1675,20 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) 
		cpuid_entry_override(entry, CPUID_24_0_EBX);

		entry->ebx |= avx10_version;



		entry->eax = 0;

		entry->ecx = 0;

		entry->edx = 0;



		/* KVM only supports up to 0x24.0x1, capped above via min(). */

		if (max_idx >= 1) {

			entry = do_host_cpuid(array, function, 1);

			if (!entry)

				goto out;



			cpuid_entry_override(entry, CPUID_24_1_ECX);

			entry->eax = 0;

			entry->ebx = 0;

			entry->edx = 0;

		}

		break;

	}

	case KVM_CPUID_SIGNATURE: {

arch/x86/kvm/reverse_cpuid.h

+4 −0
Original line number Diff line number Diff line
@@ -63,6 +63,9 @@ 
#define X86_FEATURE_AVX10_256		KVM_X86_FEATURE(CPUID_24_0_EBX, 17)

#define X86_FEATURE_AVX10_512		KVM_X86_FEATURE(CPUID_24_0_EBX, 18)



/* Intel-defined sub-features, CPUID level 0x00000024:1 (ECX) */

#define X86_FEATURE_AVX10_VNNI_INT	KVM_X86_FEATURE(CPUID_24_1_ECX, 2)



/* CPUID level 0x80000007 (EDX). */

#define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
@@ -105,6 +108,7 @@ static const struct cpuid_reg reverse_cpuid[] = { 
	[CPUID_8000_0021_ECX] = {0x80000021, 0, CPUID_ECX},

	[CPUID_7_1_ECX]       = {         7, 1, CPUID_ECX},

	[CPUID_1E_1_EAX]      = {      0x1e, 1, CPUID_EAX},

	[CPUID_24_1_ECX]      = {      0x24, 1, CPUID_ECX},

};



/*