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Message-Id: <20221125125845.1182922-4-jiaxi.chen@linux.intel.com>
Date: Fri, 25 Nov 2022 20:58:40 +0800
From: Jiaxi Chen <jiaxi.chen@...ux.intel.com>
To: kvm@...r.kernel.org
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
seanjc@...gle.com, pbonzini@...hat.com, ndesaulniers@...gle.com,
alexandre.belloni@...tlin.com, peterz@...radead.org,
jpoimboe@...nel.org, chang.seok.bae@...el.com,
pawan.kumar.gupta@...ux.intel.com, babu.moger@....com,
jmattson@...gle.com, sandipan.das@....com, tony.luck@...el.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, fenghua.yu@...el.com,
keescook@...omium.org, nathan@...nel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v5 3/8] x86: KVM: Advertise CMPccXADD CPUID to user space
CMPccXADD is a new set of instructions in the latest Intel platform
Sierra Forest. This new instruction set includes a semaphore operation
that can compare and add the operands if condition is met, which can
improve database performance.
The bit definition:
CPUID.(EAX=7,ECX=1):EAX[bit 7]
CMPccXADD is on an expected-dense CPUID leaf and some other bits on this
leaf have kernel usages. Given that, define this feature bit like
X86_FEATURE_<name> in kernel. Considering CMPccXADD itself has no truly
kernel usages and /proc/cpuinfo has too much unreadable flags, hide this
one in /proc/cpuinfo.
Advertise CMPCCXADD to KVM userspace. This is safe because there are no
new VMX controls or additional host enabling required for guests to use
this feature.
Signed-off-by: Jiaxi Chen <jiaxi.chen@...ux.intel.com>
Acked-by: Borislav Petkov <bp@...e.de>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kvm/cpuid.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index b71f4f2ecdd5..5cdd57133d90 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -308,6 +308,7 @@
/* 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_CMPCCXADD (12*32+ 7) /* "" CMPccXADD instructions */
/* 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 a3adac48766b..f8bf4fb30b96 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -663,7 +663,7 @@ void kvm_set_cpu_caps(void)
kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);
kvm_cpu_cap_mask(CPUID_7_1_EAX,
- F(AVX_VNNI) | F(AVX512_BF16)
+ F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD)
);
kvm_cpu_cap_mask(CPUID_D_1_EAX,
--
2.27.0
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