Messages in this thread Patch in this message | | | Date | Tue, 15 Nov 2022 21:50:51 +0800 | Subject | Re: [PATCH v3 1/7] x86: KVM: Move existing x86 CPUID leaf [CPUID_7_1_EAX] to kvm-only leaf | From | Xiaoyao Li <> |
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On 11/10/2022 9:52 AM, Jiaxi Chen wrote: > cpuid_leaf[12] CPUID_7_1_EAX has only two bits are in use currently: > > - AVX-VNNI CPUID.(EAX=7,ECX=1):EAX[bit 4] > - AVX512-BF16 CPUID.(EAX=7,ECX=1):EAX[bit 5] > > These two bits have no other kernel usages other than the guest > CPUID advertisement in KVM. Given that and to save space for kernel > feature bits, move these two bits to the kvm-only subleaves. The > existing leaf cpuid_leafs[12] is set to CPUID_LNX_5 so future feature > can pick it. This basically reverts: > > - commit b85a0425d805 ("Enumerate AVX Vector Neural Network > instructions") > - commit b302e4b176d0 ("x86/cpufeatures: Enumerate the new AVX512 > BFLOAT16 instructions") > - commit 1085a6b585d7 ("KVM: Expose AVX_VNNI instruction to guset")
FYI, LAM support has been queued in tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=aa387b1b1e666cacffc0b7ac7e0949a68013b2d9
It adds
+#define X86_FEATURE_LAM (12*32+26) /* Linear Address Masking */
and conflict with this patch.
Seen from the ISE, there are more bits defined in CPUID_7_1_EAX. And I believe Intel will define more and it's likely some of them will be used by kernel just like LAM.
> Signed-off-by: Jiaxi Chen <jiaxi.chen@linux.intel.com> > --- > arch/x86/include/asm/cpufeature.h | 2 +- > arch/x86/include/asm/cpufeatures.h | 4 +--- > arch/x86/kernel/cpu/common.c | 6 ------ > arch/x86/kernel/cpu/cpuid-deps.c | 1 - > arch/x86/kvm/cpuid.c | 2 +- > arch/x86/kvm/reverse_cpuid.h | 5 +++++ > 6 files changed, 8 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index 1a85e1fb0922..b2905ddd7ab4 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -24,7 +24,7 @@ enum cpuid_leafs > CPUID_7_0_EBX, > CPUID_D_1_EAX, > CPUID_LNX_4, > - CPUID_7_1_EAX, > + CPUID_LNX_5, > CPUID_8000_0008_EBX, > CPUID_6_EAX, > CPUID_8000_000A_EDX, > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > index b71f4f2ecdd5..ec468d6eaf06 100644 > --- a/arch/x86/include/asm/cpufeatures.h > +++ b/arch/x86/include/asm/cpufeatures.h > @@ -305,9 +305,7 @@ > #define X86_FEATURE_USE_IBPB_FW (11*32+16) /* "" Use IBPB during runtime firmware calls */ > #define X86_FEATURE_RSB_VMEXIT_LITE (11*32+17) /* "" Fill RSB on VM exit when EIBRS is enabled */ > > -/* 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 */ > +/* Linux-defined mapping, word 12 */ > > /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */ > #define X86_FEATURE_CLZERO (13*32+ 0) /* CLZERO instruction */ > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 3e508f239098..0c19c84d7ba0 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1026,12 +1026,6 @@ void get_cpu_cap(struct cpuinfo_x86 *c) > c->x86_capability[CPUID_7_0_EBX] = ebx; > c->x86_capability[CPUID_7_ECX] = ecx; > c->x86_capability[CPUID_7_EDX] = edx; > - > - /* Check valid sub-leaf index before accessing it */ > - if (eax >= 1) { > - cpuid_count(0x00000007, 1, &eax, &ebx, &ecx, &edx); > - c->x86_capability[CPUID_7_1_EAX] = eax; > - } > } > > /* Extended state features: level 0x0000000d */ > diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c > index c881bcafba7d..a88e0e8c39fa 100644 > --- a/arch/x86/kernel/cpu/cpuid-deps.c > +++ b/arch/x86/kernel/cpu/cpuid-deps.c > @@ -68,7 +68,6 @@ static const struct cpuid_dep cpuid_deps[] = { > { X86_FEATURE_CQM_OCCUP_LLC, X86_FEATURE_CQM_LLC }, > { X86_FEATURE_CQM_MBM_TOTAL, X86_FEATURE_CQM_LLC }, > { X86_FEATURE_CQM_MBM_LOCAL, X86_FEATURE_CQM_LLC }, > - { X86_FEATURE_AVX512_BF16, X86_FEATURE_AVX512VL }, > { X86_FEATURE_AVX512_FP16, X86_FEATURE_AVX512BW }, > { X86_FEATURE_ENQCMD, X86_FEATURE_XSAVES }, > { X86_FEATURE_PER_THREAD_MBA, X86_FEATURE_MBA }, > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 7065462378e2..89f5e7f0402b 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -656,7 +656,7 @@ void kvm_set_cpu_caps(void) > if (boot_cpu_has(X86_FEATURE_AMD_SSBD)) > kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD); > > - kvm_cpu_cap_mask(CPUID_7_1_EAX, > + kvm_cpu_cap_init_scattered(CPUID_7_1_EAX, > F(AVX_VNNI) | F(AVX512_BF16) > ); > > diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h > index a19d473d0184..674de5b24f8d 100644 > --- a/arch/x86/kvm/reverse_cpuid.h > +++ b/arch/x86/kvm/reverse_cpuid.h > @@ -13,6 +13,7 @@ > */ > enum kvm_only_cpuid_leafs { > CPUID_12_EAX = NCAPINTS, > + CPUID_7_1_EAX, > NR_KVM_CPU_CAPS, > > NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS, > @@ -24,6 +25,10 @@ enum kvm_only_cpuid_leafs { > #define KVM_X86_FEATURE_SGX1 KVM_X86_FEATURE(CPUID_12_EAX, 0) > #define KVM_X86_FEATURE_SGX2 KVM_X86_FEATURE(CPUID_12_EAX, 1) > > +/* Intel-defined sub-features, CPUID level 0x00000007:1 (EAX) */ > +#define X86_FEATURE_AVX_VNNI KVM_X86_FEATURE(CPUID_7_1_EAX, 4) > +#define X86_FEATURE_AVX512_BF16 KVM_X86_FEATURE(CPUID_7_1_EAX, 5) > + > struct cpuid_reg { > u32 function; > u32 index;
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