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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id m68sm1081837wme.48.2020.02.24.14.08.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 14:08:31 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson Cc: Paolo Bonzini , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 43/61] KVM: x86: Use KVM cpu caps to mark CR4.LA57 as not-reserved In-Reply-To: <20200201185218.24473-44-sean.j.christopherson@intel.com> References: <20200201185218.24473-1-sean.j.christopherson@intel.com> <20200201185218.24473-44-sean.j.christopherson@intel.com> Date: Mon, 24 Feb 2020 23:08:30 +0100 Message-ID: <8736azocyp.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Sean Christopherson writes: > Add accessor(s) for KVM cpu caps and use said accessor to detect > hardware support for LA57 instead of manually querying CPUID. > > No functional change intended. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/cpuid.h | 13 +++++++++++++ > arch/x86/kvm/x86.c | 2 +- > 2 files changed, 14 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h > index 7b71ae0ca05e..5ce4219d465f 100644 > --- a/arch/x86/kvm/cpuid.h > +++ b/arch/x86/kvm/cpuid.h > @@ -274,6 +274,19 @@ static __always_inline void kvm_cpu_cap_set(unsigned x86_feature) > kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature); > } > > +static __always_inline u32 kvm_cpu_cap_get(unsigned x86_feature) > +{ > + unsigned x86_leaf = x86_feature / 32; > + > + reverse_cpuid_check(x86_leaf); > + return kvm_cpu_caps[x86_leaf] & __feature_bit(x86_feature); > +} > + > +static __always_inline bool kvm_cpu_cap_has(unsigned x86_feature) > +{ > + return kvm_cpu_cap_get(x86_feature); > +} I know this works (and I even checked C99 to make sure that it works not by accident) but I have to admit that explicit '!!' conversion to bool always makes me feel safer :-) > + > static __always_inline void kvm_cpu_cap_check_and_set(unsigned x86_feature) > { > if (boot_cpu_has(x86_feature)) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c5ed199d6cd9..cb40737187a1 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -912,7 +912,7 @@ static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c) > { > u64 reserved_bits = __cr4_reserved_bits(cpu_has, c); > > - if (cpuid_ecx(0x7) & feature_bit(LA57)) > + if (kvm_cpu_cap_has(X86_FEATURE_LA57)) > reserved_bits &= ~X86_CR4_LA57; > > if (kvm_x86_ops->umip_emulated()) Reviewed-by: Vitaly Kuznetsov -- Vitaly