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Thu, 04 Jul 2024 18:25:40 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGEF2U1YD+6q18JF3TqogZJNBg0f79mJvZ/g7DB4yQv9lBC9AAPfmiWQZkt3CycumfSymUOXQ== X-Received: by 2002:ad4:5ba4:0:b0:6b5:e099:4d69 with SMTP id 6a1803df08f44-6b5ecfb9422mr31683186d6.26.1720142740270; Thu, 04 Jul 2024 18:25:40 -0700 (PDT) Received: from starship ([2607:fea8:fc01:7b7f:6adb:55ff:feaa:b156]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6b59e5f2b77sm69034896d6.92.2024.07.04.18.25.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jul 2024 18:25:40 -0700 (PDT) Message-ID: <43ef06aca700528d956c8f51101715df86f32a91.camel@redhat.com> Subject: Re: [PATCH v2 22/49] KVM: x86: Add a macro to precisely handle aliased 0x1.EDX CPUID features From: Maxim Levitsky To: Sean Christopherson , Paolo Bonzini , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Hou Wenlong , Kechen Lu , Oliver Upton , Binbin Wu , Yang Weijiang , Robert Hoo Date: Thu, 04 Jul 2024 21:25:39 -0400 In-Reply-To: <20240517173926.965351-23-seanjc@google.com> References: <20240517173926.965351-1-seanjc@google.com> <20240517173926.965351-23-seanjc@google.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit On Fri, 2024-05-17 at 10:38 -0700, Sean Christopherson wrote: > Add a macro to precisely handle CPUID features that AMD duplicated from > CPUID.0x1.EDX into CPUID.0x8000_0001.EDX. This will allow adding an > assert that all features passed to kvm_cpu_cap_init() match the word being > processed, e.g. to prevent passing a feature from CPUID 0x7 to CPUID 0x1. > > Because the kernel simply reuses the X86_FEATURE_* definitions from > CPUID.0x1.EDX, KVM's use of the aliased features would result in false > positives from such an assert. > > No functional change intended. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/cpuid.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 5e3b97d06374..f2bd2f5c4ea3 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -88,6 +88,16 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted) > F(name); \ > }) > > +/* > + * Aliased Features - For features in 0x8000_0001.EDX that are duplicates of > + * identical 0x1.EDX features, and thus are aliased from 0x1 to 0x8000_0001. > + */ > +#define AF(name) \ > +({ \ > + BUILD_BUG_ON(__feature_leaf(X86_FEATURE_##name) != CPUID_1_EDX); \ > + feature_bit(name); \ > +}) > + > /* > * Magic value used by KVM when querying userspace-provided CPUID entries and > * doesn't care about the CPIUD index because the index of the function in > @@ -758,13 +768,13 @@ void kvm_set_cpu_caps(void) > ); > > kvm_cpu_cap_init(CPUID_8000_0001_EDX, > - F(FPU) | F(VME) | F(DE) | F(PSE) | > - F(TSC) | F(MSR) | F(PAE) | F(MCE) | > - F(CX8) | F(APIC) | 0 /* Reserved */ | F(SYSCALL) | > - F(MTRR) | F(PGE) | F(MCA) | F(CMOV) | > - F(PAT) | F(PSE36) | 0 /* Reserved */ | > - F(NX) | 0 /* Reserved */ | F(MMXEXT) | F(MMX) | > - F(FXSR) | F(FXSR_OPT) | X86_64_F(GBPAGES) | F(RDTSCP) | > + AF(FPU) | AF(VME) | AF(DE) | AF(PSE) | > + AF(TSC) | AF(MSR) | AF(PAE) | AF(MCE) | > + AF(CX8) | AF(APIC) | 0 /* Reserved */ | F(SYSCALL) | > + AF(MTRR) | AF(PGE) | AF(MCA) | AF(CMOV) | > + AF(PAT) | AF(PSE36) | 0 /* Reserved */ | > + F(NX) | 0 /* Reserved */ | F(MMXEXT) | AF(MMX) | > + AF(FXSR) | F(FXSR_OPT) | X86_64_F(GBPAGES) | F(RDTSCP) | > 0 /* Reserved */ | X86_64_F(LM) | F(3DNOWEXT) | F(3DNOW) > ); > Hi, What if we defined the aliased features instead. Something like this: #define __X86_FEATURE_8000_0001_ALIAS(feature) \ (feature + (CPUID_8000_0001_EDX - CPUID_1_EDX) * 32) #define KVM_X86_FEATURE_FPU_ALIAS __X86_FEATURE_8000_0001_ALIAS(KVM_X86_FEATURE_FPU) #define KVM_X86_FEATURE_VME_ALIAS __X86_FEATURE_8000_0001_ALIAS(KVM_X86_FEATURE_VME) And then just use for example the 'F(FPU_ALIAS)' in the CPUID_8000_0001_EDX Best regards, Maxim Levitsky