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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id z22sm10267401edm.57.2021.05.24.06.54.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 May 2021 06:54:23 -0700 (PDT) Subject: Re: [PATCH v2 1/7] KVM: nVMX: Introduce nested_evmcs_is_used() To: Vitaly Kuznetsov , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Maxim Levitsky , linux-kernel@vger.kernel.org References: <20210517135054.1914802-1-vkuznets@redhat.com> <20210517135054.1914802-2-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: <115fcae7-0c88-4865-6494-bdf6fb672382@redhat.com> Date: Mon, 24 May 2021 15:54:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210517135054.1914802-2-vkuznets@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/05/21 15:50, Vitaly Kuznetsov wrote: > Unlike regular set_current_vmptr(), nested_vmx_handle_enlightened_vmptrld() > can not be called directly from vmx_set_nested_state() as KVM may not have > all the information yet (e.g. HV_X64_MSR_VP_ASSIST_PAGE MSR may not be > restored yet). Enlightened VMCS is mapped later while getting nested state > pages. In the meantime, vmx->nested.hv_evmcs remains NULL and using it > for various checks is incorrect. In particular, if KVM_GET_NESTED_STATE is > called right after KVM_SET_NESTED_STATE, KVM_STATE_NESTED_EVMCS flag in the > resulting state will be unset (and such state will later fail to load). > > Introduce nested_evmcs_is_used() and use 'is_guest_mode(vcpu) && > vmx->nested.current_vmptr == -1ull' check to detect not-yet-mapped eVMCS > after restore. > > Signed-off-by: Vitaly Kuznetsov Would it make sense to instead use hv_evmcs_ptr, making the unused value -1 instead of 0? I even had this untested patch already lying around as a cleanup I never bothered to submit: diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index a19cfcb625da..dd3e4ddaaf26 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -187,7 +187,7 @@ static int nested_vmx_fail(struct kvm_vcpu *vcpu, u32 vm_instruction_error) * failValid writes the error number to the current VMCS, which * can't be done if there isn't a current VMCS. */ - if (vmx->nested.current_vmptr == -1ull && !vmx->nested.hv_evmcs) + if (vmx->nested.current_vmptr == -1ull && vmx->nested.hv_evmcs_vmptr == -1) return nested_vmx_failInvalid(vcpu); return nested_vmx_failValid(vcpu, vm_instruction_error); @@ -221,11 +221,11 @@ static inline void nested_release_evmcs(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); - if (!vmx->nested.hv_evmcs) + if (vmx->nested.hv_evmcs_vmptr == -1) return; kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map, NULL, true); - vmx->nested.hv_evmcs_vmptr = 0; + vmx->nested.hv_evmcs_vmptr = -1; vmx->nested.hv_evmcs = NULL; } @@ -1978,10 +1978,8 @@ static enum nested_evmptrld_status nested_vmx_handle_enlightened_vmptrld( if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa)) return EVMPTRLD_DISABLED; - if (unlikely(!vmx->nested.hv_evmcs || - evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) { - if (!vmx->nested.hv_evmcs) - vmx->nested.current_vmptr = -1ull; + if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) { + vmx->nested.current_vmptr = -1ull; nested_release_evmcs(vcpu); @@ -2052,7 +2050,7 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); - if (vmx->nested.hv_evmcs) { + if (vmx->nested.hv_evmcs_vmptr != -1) { copy_vmcs12_to_enlightened(vmx); /* All fields are clean */ vmx->nested.hv_evmcs->hv_clean_fields |= @@ -2204,7 +2202,7 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) u32 exec_control; u64 guest_efer = nested_vmx_calc_efer(vmx, vmcs12); - if (vmx->nested.dirty_vmcs12 || vmx->nested.hv_evmcs) + if (vmx->nested.dirty_vmcs12 || vmx->nested.hv_evmcs_vmptr != -1) prepare_vmcs02_early_rare(vmx, vmcs12); /* @@ -2487,9 +2485,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, enum vm_entry_failure_code *entry_failure_code) { struct vcpu_vmx *vmx = to_vmx(vcpu); - struct hv_enlightened_vmcs *hv_evmcs = vmx->nested.hv_evmcs; - if (vmx->nested.dirty_vmcs12 || hv_evmcs) { + if (vmx->nested.dirty_vmcs12 || vmx->nested.hv_evmcs_vmptr != -1) { prepare_vmcs02_rare(vmx, vmcs12); vmx->nested.dirty_vmcs12 = false; } @@ -3075,7 +3072,7 @@ static bool nested_get_evmcs_page(struct kvm_vcpu *vcpu) * L2 was running), map it here to make sure vmcs12 changes are * properly reflected. */ - if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs) { + if (vmx->nested.enlightened_vmcs_enabled && vmx->nested.hv_evmcs_vmptr == -1) { enum nested_evmptrld_status evmptrld_status = nested_vmx_handle_enlightened_vmptrld(vcpu, false); @@ -3419,7 +3416,7 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, load_vmcs12_host_state(vcpu, vmcs12); vmcs12->vm_exit_reason = exit_reason.full; - if (enable_shadow_vmcs || vmx->nested.hv_evmcs) + if (enable_shadow_vmcs || vmx->nested.hv_evmcs_vmptr != -1) vmx->nested.need_vmcs12_to_shadow_sync = true; return NVMX_VMENTRY_VMEXIT; } @@ -3449,7 +3446,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) return nested_vmx_failInvalid(vcpu); } - if (CC(!vmx->nested.hv_evmcs && vmx->nested.current_vmptr == -1ull)) + if (CC(vmx->nested.hv_evmcs_vmptr == -1 && vmx->nested.current_vmptr == -1ull)) return nested_vmx_failInvalid(vcpu); vmcs12 = get_vmcs12(vcpu); @@ -3463,7 +3460,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) if (CC(vmcs12->hdr.shadow_vmcs)) return nested_vmx_failInvalid(vcpu); - if (vmx->nested.hv_evmcs) { + if (vmx->nested.hv_evmcs_vmptr != -1) { copy_enlightened_to_vmcs12(vmx); /* Enlightened VMCS doesn't have launch state */ vmcs12->launch_state = !launch; @@ -4014,10 +4011,10 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) { struct vcpu_vmx *vmx = to_vmx(vcpu); - if (vmx->nested.hv_evmcs) + if (vmx->nested.hv_evmcs_vmptr != -1) sync_vmcs02_to_vmcs12_rare(vcpu, vmcs12); - vmx->nested.need_sync_vmcs02_to_vmcs12_rare = !vmx->nested.hv_evmcs; + vmx->nested.need_sync_vmcs02_to_vmcs12_rare = (vmx->nested.hv_evmcs_vmptr == -1); vmcs12->guest_cr0 = vmcs12_guest_cr0(vcpu, vmcs12); vmcs12->guest_cr4 = vmcs12_guest_cr4(vcpu, vmcs12); @@ -4514,7 +4511,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason, } if ((vm_exit_reason != -1) && - (enable_shadow_vmcs || vmx->nested.hv_evmcs)) + (enable_shadow_vmcs || vmx->nested.hv_evmcs_vmptr != -1)) vmx->nested.need_vmcs12_to_shadow_sync = true; /* in case we halted in L2 */ @@ -5210,7 +5207,7 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu) return nested_vmx_fail(vcpu, VMXERR_VMPTRLD_VMXON_POINTER); /* Forbid normal VMPTRLD if Enlightened version was used */ - if (vmx->nested.hv_evmcs) + if (vmx->nested.hv_evmcs_vmptr != -1) return 1; if (vmx->nested.current_vmptr != vmptr) { @@ -5266,7 +5263,7 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu) if (!nested_vmx_check_permission(vcpu)) return 1; - if (unlikely(to_vmx(vcpu)->nested.hv_evmcs)) + if (unlikely(to_vmx(vcpu)->nested.hv_evmcs_vmptr != -1)) return 1; if (get_vmx_mem_address(vcpu, exit_qual, instr_info, @@ -6038,7 +6035,7 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu, if (vmx_has_valid_vmcs12(vcpu)) { kvm_state.size += sizeof(user_vmx_nested_state->vmcs12); - if (vmx->nested.hv_evmcs) + if (vmx->nested.hv_evmcs_vmptr != -1) kvm_state.flags |= KVM_STATE_NESTED_EVMCS; if (is_guest_mode(vcpu) && @@ -6094,7 +6091,7 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu, } else { copy_vmcs02_to_vmcs12_rare(vcpu, get_vmcs12(vcpu)); if (!vmx->nested.need_vmcs12_to_shadow_sync) { - if (vmx->nested.hv_evmcs) + if (vmx->nested.hv_evmcs_vmptr != -1) copy_enlightened_to_vmcs12(vmx); else if (enable_shadow_vmcs) copy_shadow_to_vmcs12(vmx); diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h index 184418baeb3c..55925be48973 100644 --- a/arch/x86/kvm/vmx/nested.h +++ b/arch/x86/kvm/vmx/nested.h @@ -63,7 +63,7 @@ static inline int vmx_has_valid_vmcs12(struct kvm_vcpu *vcpu) * have vmcs12 if it is true. */ return is_guest_mode(vcpu) || vmx->nested.current_vmptr != -1ull || - vmx->nested.hv_evmcs; + vmx->nested.hv_evmcs_vmptr != -1; } static inline u16 nested_get_vpid02(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f2fd447eed45..33208aa4ac87 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6974,6 +6974,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu) vmx->nested.posted_intr_nv = -1; vmx->nested.current_vmptr = -1ull; + vmx->nested.hv_evmcs_vmptr = -1; vcpu->arch.microcode_version = 0x100000000ULL; vmx->msr_ia32_feature_control_valid_bits = FEAT_CTL_LOCKED; Paolo