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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=tq6orQL+5MP6ahCa64iKAgWb6ZPHNMgYBOwXTD0WmjfrfJvdhlNU6yVWg1Idcr0ge MqB2ILmOWMIT/7FcBD3L/GME7qvWeDoFrMbpZYHjF4dl4/BehH7zKZNnkOf8q812y5 V9MNDsTSSJm0Ux5zISOWsNiPbETg2lRDRyVqPwUJ4BZldS3m8ZQhip9KvQBJv600F8 S5/UGHDE4Ho/qxJbHC0fIE6ykYED71KlbBvu4kyoxn/hfFLDq2JpNX1+1KvpimdZAG cXltHPy7+To/N64SUaJGpny1uEZsXPST7kK0rOYimeMb++aTUMDeFj7DAtnCSeitzk cwYl4sFY18Tlg== Message-ID: <3ec986fa-2bf0-4c78-b532-343ad19436b2@zytor.com> Date: Thu, 12 Dec 2024 10:48:01 -0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 17/27] KVM: x86: Mark CR4.FRED as not reserved when guest can use FRED To: Chao Gao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, seanjc@google.com, pbonzini@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com References: <20241001050110.3643764-1-xin@zytor.com> <20241001050110.3643764-18-xin@zytor.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/24/2024 12:18 AM, Chao Gao wrote: >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index 03f42b218554..bfdd10773136 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -8009,6 +8009,10 @@ void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) >> kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_LAM); >> kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_FRED); >> >> + /* Don't allow CR4.FRED=1 before all of FRED KVM support is in place. */ >> + if (!guest_can_use(vcpu, X86_FEATURE_FRED)) >> + vcpu->arch.cr4_guest_rsvd_bits |= X86_CR4_FRED; > > is this necessary? __kvm_is_valid_cr4() ensures that guests cannot set any bit > which isn't supported by the hardware. > > To account for hardware/KVM caps, I think the following changes will work. This > will fix all other bits besides X86_CR4_FRED. This seems a generic infra improvement, maybe it's better for you to send it as an individual patch to Sean and the KVM mailing list? > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 4a93ac1b9be9..2bec3ba8e47d 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1873,6 +1873,7 @@ struct kvm_arch_async_pf { > extern u32 __read_mostly kvm_nr_uret_msrs; > extern bool __read_mostly allow_smaller_maxphyaddr; > extern bool __read_mostly enable_apicv; > +extern u64 __read_mostly cr4_reserved_bits; > extern struct kvm_x86_ops kvm_x86_ops; > > #define kvm_x86_call(func) static_call(kvm_x86_##func) > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 2617be544480..57d82fbcfd3f 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -393,8 +393,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu); > > kvm_pmu_refresh(vcpu); > - vcpu->arch.cr4_guest_rsvd_bits = > - __cr4_reserved_bits(guest_cpuid_has, vcpu); > + vcpu->arch.cr4_guest_rsvd_bits = cr4_reserved_bits | > + __cr4_reserved_bits(guest_cpuid_has, vcpu); > > kvm_hv_set_cpuid(vcpu, kvm_cpuid_has_hyperv(vcpu->arch.cpuid_entries, > vcpu->arch.cpuid_nent)); > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 34b52b49f5e6..08b42bbd2342 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -119,7 +119,7 @@ u64 __read_mostly efer_reserved_bits = ~((u64)(EFER_SCE | EFER_LME | EFER_LMA)); > static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE); > #endif > > -static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS; > +u64 __read_mostly cr4_reserved_bits; > > #define KVM_EXIT_HYPERCALL_VALID_MASK (1 << KVM_HC_MAP_GPA_RANGE) > > @@ -1110,13 +1110,7 @@ EXPORT_SYMBOL_GPL(kvm_emulate_xsetbv); > > bool __kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) > { > - if (cr4 & cr4_reserved_bits) > - return false; > - > - if (cr4 & vcpu->arch.cr4_guest_rsvd_bits) > - return false; > - > - return true; > + return !(cr4 & vcpu->arch.cr4_guest_rsvd_bits); > } > EXPORT_SYMBOL_GPL(__kvm_is_valid_cr4); > > >> + >> vmx_setup_uret_msrs(vmx); >> >> if (cpu_has_secondary_exec_ctrls()) >> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h >> index 992e73ee2ec5..0ed91512b757 100644 >> --- a/arch/x86/kvm/x86.h >> +++ b/arch/x86/kvm/x86.h >> @@ -561,6 +561,8 @@ enum kvm_msr_access { >> __reserved_bits |= X86_CR4_PCIDE; \ >> if (!__cpu_has(__c, X86_FEATURE_LAM)) \ >> __reserved_bits |= X86_CR4_LAM_SUP; \ >> + if (!__cpu_has(__c, X86_FEATURE_FRED)) \ >> + __reserved_bits |= X86_CR4_FRED; \ >> __reserved_bits; \ >> }) >> >> -- >> 2.46.2 >> >>