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AJvYcCU+3UFlQ1DJjIaYiUIzHWuogRhrj7Gx/pgvXKzd9lYYtcOyTCLiwoHepmPwDsBhCNy+U/PrSCKMmV3V90s=@vger.kernel.org X-Gm-Message-State: AOJu0Yzb8CYtYKcx/RgUTMlPu4gGfRJ1PS+8/E5c/uiseK+v8OhzCLPQ 7qIA8P2HC9jf2aRQ77FDjP4YHf0l4CcTNvUNZPTDjgkd1omuJJ5hjKjAVTUD5t3yW5OfoN0RwZe qQgCTLw== X-Google-Smtp-Source: AGHT+IHa5GABwEH2tlBdSM74mYDSBbfkFweBmt+8WvoWz8syzYPBNcgs9/zm7V7+ssuMso/wSieQoqXZVOg= X-Received: from pjnu19.prod.google.com ([2002:a17:90a:8913:b0:34c:4048:b62b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:35c8:b0:340:e521:bc73 with SMTP id 98e67ed59e1d1-34abd6cc48fmr12942643a91.5.1765982463248; Wed, 17 Dec 2025 06:41:03 -0800 (PST) Date: Wed, 17 Dec 2025 06:41:01 -0800 In-Reply-To: <70FDA8A5-9B92-459B-A661-159365AE6385@zytor.com> 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> <70FDA8A5-9B92-459B-A661-159365AE6385@zytor.com> Message-ID: Subject: Re: [PATCH] KVM: nVMX: Disallow access to vmcs12 fields that aren't supported by "hardware" From: Sean Christopherson To: Xin Li Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="us-ascii" On Tue, Dec 16, 2025, Xin Li wrote: > > diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c > > index 4233b5ca9461..78eca9399975 100644 > > --- a/arch/x86/kvm/vmx/vmcs12.c > > +++ b/arch/x86/kvm/vmx/vmcs12.c > > @@ -9,7 +9,7 @@ > > FIELD(number, name), \ > > [ROL16(number##_HIGH, 6)] = VMCS12_OFFSET(name) + sizeof(u32) > > > > -const unsigned short vmcs12_field_offsets[] = { > > +const __initconst u16 supported_vmcs12_field_offsets[] = { > > I initially misunderstood "supported" to mean the VMCS fields available at > runtime. I'm unsure if it's necessary to make its meaning more explicit. > E.g., prefix with kvm_? Oh, good point. Ya, will do. > > FIELD(VIRTUAL_PROCESSOR_ID, virtual_processor_id), > > FIELD(POSTED_INTR_NV, posted_intr_nv), > > FIELD(GUEST_ES_SELECTOR, guest_es_selector), > > @@ -158,4 +158,55 @@ const unsigned short vmcs12_field_offsets[] = { > > FIELD(HOST_SSP, host_ssp), > > FIELD(HOST_INTR_SSP_TABLE, host_ssp_tbl), > > }; > > -const unsigned int nr_vmcs12_fields = ARRAY_SIZE(vmcs12_field_offsets); > > + > > +u16 vmcs12_field_offsets[ARRAY_SIZE(supported_vmcs12_field_offsets)] __ro_after_init; > > +unsigned int nr_vmcs12_fields __ro_after_init; > > + > > +#define VMCS12_CASE64(enc) case enc##_HIGH: case enc > > + > > +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(); > > Combine the above 2 cases? > > > + 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(); > > Combine all CET cases? Yeah, will do. I was on the fence as to whether it would be a net positive to combine them. Thanks!