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AJvYcCXblvstaZHfV4xHcfMefRc404N6qTD+eUVsTl1/nJ1SoSvW3psjStYkjXwBNVIiMVlUncOL83wqE3GJmVTef9pXmqRz X-Gm-Message-State: AOJu0YxlgLSURWeu9IP3pSvoVFna0WmTfa1a3aj5gxPoY7qi223XfjY/ Y7k4/B1MnmERGgFcBotL0KFx/nVEu6fslG/+cMS8CYf68F+LoV8GdmI+NSbtG5vBMuduw/OrPnc 76g== X-Google-Smtp-Source: AGHT+IHkvvRyR4ZOFfRZbvHxisjAesK2LtdhCRlJFAR3MmJzlIQfXGNakxdxfoHY0k35gPGuOg9STWf3aHI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:f0b:b0:de5:2325:72dc with SMTP id et11-20020a0569020f0b00b00de5232572dcmr988315ybb.5.1714596230054; Wed, 01 May 2024 13:43:50 -0700 (PDT) Date: Wed, 1 May 2024 13:43:48 -0700 In-Reply-To: <20240219074733.122080-14-weijiang.yang@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240219074733.122080-1-weijiang.yang@intel.com> <20240219074733.122080-14-weijiang.yang@intel.com> Message-ID: Subject: Re: [PATCH v10 13/27] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS From: Sean Christopherson To: Yang Weijiang Cc: pbonzini@redhat.com, dave.hansen@intel.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org, chao.gao@intel.com, rick.p.edgecombe@intel.com, mlevitsk@redhat.com, john.allen@amd.com, Zhang Yi Z Content-Type: text/plain; charset="us-ascii" On Sun, Feb 18, 2024, Yang Weijiang wrote: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 9eb5c8dbd4fb..b502d68a2576 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3926,16 +3926,23 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > } > break; > case MSR_IA32_XSS: > - if (!msr_info->host_initiated && > - !guest_cpuid_has(vcpu, X86_FEATURE_XSAVES)) > + /* > + * If KVM reported support of XSS MSR, even guest CPUID doesn't > + * support XSAVES, still allow userspace to set default value(0) > + * to this MSR. > + */ > + if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVES) && > + !(msr_info->host_initiated && data == 0)) With my proposed MSR access cleanup[*], I think (hope?) this simply becomes: if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVES)) return KVM_MSR_RET_UNSUPPORTED; with no comment needed as the "host && !data" case is handled in common code. [*] https://lore.kernel.org/all/20240425181422.3250947-1-seanjc@google.com