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AJvYcCXY6ijIXrjSUgcHxeWxl1bS1dyYNmXUA2LW4/7svq7cpDyHF93+zpX/g0hrKs3do9JTuahYODeLOo3uL5c=@vger.kernel.org X-Gm-Message-State: AOJu0YwOjMCUwbBdzhVlTSK9y6v5nXnm66sBgQOmxu1gO6WIUGiMeoSd bQfv2Yv1yTz+qRaz8E6HGbheo1Wb+ov7KKSusBNkKRibu367kKglzZDW57sWRFUKOttkcKxZfsU KttTeMA== X-Google-Smtp-Source: AGHT+IGY1sNiClwBZTcmK97/eMChbdF+koURDQ4b/nqndAH0Pf6+wiOIfdVBF86RlKu8osKt9rWO6gJhKmc= X-Received: from pjn14.prod.google.com ([2002:a17:90b:570e:b0:30a:7da4:f075]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4c11:b0:312:26d9:d5b4 with SMTP id 98e67ed59e1d1-3159d8c7e55mr28632166a91.17.1750778408771; Tue, 24 Jun 2025 08:20:08 -0700 (PDT) Date: Tue, 24 Jun 2025 08:20:07 -0700 In-Reply-To: <20250328171205.2029296-4-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250328171205.2029296-1-xin@zytor.com> <20250328171205.2029296-4-xin@zytor.com> Message-ID: Subject: Re: [PATCH v4 03/19] KVM: VMX: Disable FRED if FRED consistency checks fail From: Sean Christopherson To: "Xin Li (Intel)" Cc: pbonzini@redhat.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, andrew.cooper3@citrix.com, luto@kernel.org, peterz@infradead.org, chao.gao@intel.com, xin3.li@intel.com Content-Type: text/plain; charset="us-ascii" On Fri, Mar 28, 2025, Xin Li (Intel) wrote: > From: Xin Li > > Do not virtualize FRED if FRED consistency checks fail. > > Either on broken hardware, or when run KVM on top of another hypervisor > before the underlying hypervisor implements nested FRED correctly. > > Suggested-by: Chao Gao > Signed-off-by: Xin Li > Signed-off-by: Xin Li (Intel) > Tested-by: Shan Kang > Reviewed-by: Chao Gao > --- > > Change in v4: > * Call out the reason why not check FRED VM-exit controls in > cpu_has_vmx_fred() (Chao Gao). > --- > arch/x86/kvm/vmx/capabilities.h | 11 +++++++++++ > arch/x86/kvm/vmx/vmx.c | 3 +++ > 2 files changed, 14 insertions(+) > > diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h > index b2aefee59395..b4f49a4690ca 100644 > --- a/arch/x86/kvm/vmx/capabilities.h > +++ b/arch/x86/kvm/vmx/capabilities.h > @@ -400,6 +400,17 @@ static inline bool vmx_pebs_supported(void) > return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept; > } > > +static inline bool cpu_has_vmx_fred(void) > +{ > + /* > + * setup_vmcs_config() guarantees FRED VM-entry/exit controls > + * are either all set or none. So, no need to check FRED VM-exit > + * controls. > + */ > + return cpu_feature_enabled(X86_FEATURE_FRED) && Drop the cpu_feature_enabled(). These helpers are all about checking raw CPU support; whether or not the kernel is configured to support FRED is irrelevant. [For these helpers; KVM obviously needs to account for FRED support in other paths, but that should be automagically handled by kvm_set_cpu_caps()] > + (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED); > +} > + > static inline bool cpu_has_notify_vmexit(void) > { > return vmcs_config.cpu_based_2nd_exec_ctrl & > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index e38545d0dd17..ab84939ace96 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -8052,6 +8052,9 @@ static __init void vmx_set_cpu_caps(void) > kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64); > } > > + if (!cpu_has_vmx_fred()) > + kvm_cpu_cap_clear(X86_FEATURE_FRED); > + > if (!enable_pmu) > kvm_cpu_cap_clear(X86_FEATURE_PDCM); > kvm_caps.supported_perf_cap = vmx_get_perf_capabilities(); > -- > 2.48.1 >