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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.googlemail.com with ESMTPSA id go40-20020a1709070da800b006dfc3945312sm614245ejc.202.2022.03.18.09.29.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Mar 2022 09:29:21 -0700 (PDT) Message-ID: <1dc56110-5f1b-6140-937c-bf4a28ddbe87@redhat.com> Date: Fri, 18 Mar 2022 17:29:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v3 6/6] KVM: x86: allow defining return-0 static calls Content-Language: en-US To: Maxim Levitsky , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Peter Zijlstra Cc: seanjc@google.com References: <20220217180831.288210-1-pbonzini@redhat.com> <20220217180831.288210-7-pbonzini@redhat.com> <3bbe3f8717cdf122f909a48e117dab6c09d8e0c8.camel@redhat.com> From: Paolo Bonzini In-Reply-To: <3bbe3f8717cdf122f909a48e117dab6c09d8e0c8.camel@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/17/22 18:43, Maxim Levitsky wrote: > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h > index 20f64e07e359..3388072b2e3b 100644 > --- a/arch/x86/include/asm/kvm-x86-ops.h > +++ b/arch/x86/include/asm/kvm-x86-ops.h > @@ -88,7 +88,7 @@ KVM_X86_OP(deliver_interrupt) > KVM_X86_OP_OPTIONAL(sync_pir_to_irr) > KVM_X86_OP_OPTIONAL_RET0(set_tss_addr) > KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr) > -KVM_X86_OP_OPTIONAL_RET0(get_mt_mask) > +KVM_X86_OP(get_mt_mask) > KVM_X86_OP(load_mmu_pgd) > KVM_X86_OP(has_wbinvd_exit) > KVM_X86_OP(get_l2_tsc_offset) > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index a09b4f1a18f6..0c09292b0611 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -4057,6 +4057,11 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index) > return true; > } > > +static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) > +{ > + return 0; > +} > + > static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > { > struct vcpu_svm *svm = to_svm(vcpu); > @@ -4718,6 +4723,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { > .check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons, > .apicv_post_state_restore = avic_apicv_post_state_restore, > > + .get_mt_mask = svm_get_mt_mask, > .get_exit_info = svm_get_exit_info, > > .vcpu_after_set_cpuid = svm_vcpu_after_set_cpuid, Thanks, I'll send it as a complete patch. Please reply there with your Signed-off-by. Related to this, I don't see anything in arch/x86/kernel/static_call.c that limits this code to x86-64: if (func == &__static_call_return0) { emulate = code; code = &xor5rax; } On 32-bit, it will be patched as "dec ax; xor eax, eax" or something like that. Fortunately it doesn't corrupt any callee-save register but it is not just a bit funky, it's also not a single instruction. Paolo