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AJvYcCVdMCl68NXD4PEkH9jBMprPBSnOFKwyv5Rhqdu7Ow1tuulfOcRl0Yn53r6vQ/CFD3sb8xlkXo86llwxBEM=@vger.kernel.org X-Gm-Message-State: AOJu0Yzwy41extvptDhy/soSttU3v3gFbog3jLm9SH70GaHWabQ7kh1T C7m9YleLgGhzr6MKvz+254w/SoAWQ5FqRKZq3dAmBP70trVFR3LYPQf0I1lbiO5BaG5DjE/l9D/ JkhpEhw== X-Google-Smtp-Source: AGHT+IFgoiSRhCa2DGqzmwKewI52pPql69AlIaj8ohvOK+OVLpF3ooUoJXmlDlOgZajNtUgMUInbNQ5aMKk= X-Received: from pjbnc15.prod.google.com ([2002:a17:90b:37cf:b0:340:631a:67fb]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1dc6:b0:34a:b8e0:dd59 with SMTP id 98e67ed59e1d1-34abd6e0451mr17003159a91.15.1765982288210; Wed, 17 Dec 2025 06:38:08 -0800 (PST) Date: Wed, 17 Dec 2025 06:38:06 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251216012918.1707681-1-seanjc@google.com> Message-ID: Subject: Re: [PATCH] KVM: nVMX: Disallow access to vmcs12 fields that aren't supported by "hardware" From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="us-ascii" On Wed, Dec 17, 2025, Chao Gao wrote: > >+static __init bool cpu_has_vmcs12_field(unsigned int idx) > >+{ > >+ switch (VMCS12_IDX_TO_ENC(idx)) { > >+ case VIRTUAL_PROCESSOR_ID: return cpu_has_vmx_vpid(); > >+ case POSTED_INTR_NV: return cpu_has_vmx_posted_intr(); > >+ VMCS12_CASE64(TSC_MULTIPLIER): return cpu_has_vmx_tsc_scaling(); > >+ VMCS12_CASE64(VIRTUAL_APIC_PAGE_ADDR): return cpu_has_vmx_tpr_shadow(); > >+ VMCS12_CASE64(APIC_ACCESS_ADDR): return cpu_has_vmx_virtualize_apic_accesses(); > >+ VMCS12_CASE64(POSTED_INTR_DESC_ADDR): return cpu_has_vmx_posted_intr(); > >+ VMCS12_CASE64(VM_FUNCTION_CONTROL): return cpu_has_vmx_vmfunc(); > >+ VMCS12_CASE64(EPT_POINTER): return cpu_has_vmx_ept(); > >+ VMCS12_CASE64(EPTP_LIST_ADDRESS): return cpu_has_vmx_vmfunc(); > >+ VMCS12_CASE64(XSS_EXIT_BITMAP): return cpu_has_vmx_xsaves(); > >+ VMCS12_CASE64(ENCLS_EXITING_BITMAP): return cpu_has_vmx_encls_vmexit(); > >+ VMCS12_CASE64(GUEST_IA32_PERF_GLOBAL_CTRL): return cpu_has_load_perf_global_ctrl(); > >+ VMCS12_CASE64(HOST_IA32_PERF_GLOBAL_CTRL): return cpu_has_load_perf_global_ctrl(); > >+ case TPR_THRESHOLD: return cpu_has_vmx_tpr_shadow(); > >+ case SECONDARY_VM_EXEC_CONTROL: return cpu_has_secondary_exec_ctrls(); > >+ case GUEST_S_CET: return cpu_has_load_cet_ctrl(); > >+ case GUEST_SSP: return cpu_has_load_cet_ctrl(); > >+ case GUEST_INTR_SSP_TABLE: return cpu_has_load_cet_ctrl(); > >+ case HOST_S_CET: return cpu_has_load_cet_ctrl(); > >+ case HOST_SSP: return cpu_has_load_cet_ctrl(); > >+ case HOST_INTR_SSP_TABLE: return cpu_has_load_cet_ctrl(); > > Most fields here are not shadowed, e.g., CET-related fields. So, the plan is > that new fields should be added here regardless of whether they are shadowed or > not, right? Yep. It'll be mildly annoying to keep up-to-date, but I hopefully having an "unconditional" rule will be less confusing than limiting the checks to fields that are allowed to hit the shadow VMCS. > And GUEST_INTR_STATUS is missing here. It depends on APICv and is handled > explicitly in init_vmcs_shadow_fields(). Gah, I had that one on my todo list, but got sidetracked for a week and completely forgot about it. Thank you!