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[52.49.196.232]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42cb7f363e4sm10484180f8f.12.2025.11.21.03.11.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Nov 2025 03:11:26 -0800 (PST) From: Fred Griffoul To: kvm@vger.kernel.org Cc: seanjc@google.com, pbonzini@redhat.com, vkuznets@redhat.com, shuah@kernel.org, dwmw@amazon.co.uk, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Fred Griffoul Subject: [PATCH v3 03/10] KVM: x86: Add nested state validation for pfncache support Date: Fri, 21 Nov 2025 11:11:06 +0000 Message-ID: <20251121111113.456628-4-griffoul@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251121111113.456628-1-griffoul@gmail.com> References: <20251121111113.456628-1-griffoul@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Fred Griffoul Implement state validation for nested virtualization to enable pfncache support for L1 guest pages. This adds a new nested_ops callback 'is_nested_state_invalid()' that detects when KVM needs to reload nested virtualization state. A KVM_REQ_GET_NESTED_STATE_PAGES request is triggered to reload affected pages before L2 execution when it detects invalid state. The callback monitors L1 guest pages during guest entry/exit while the vCPU runs in IN_GUEST_MODE. Currently, VMX implementations return false, with full support planned for the next patch. Signed-off-by: Fred Griffoul --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/vmx/nested.c | 6 ++++++ arch/x86/kvm/x86.c | 14 +++++++++++++- 3 files changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index 48598d017d6f..4675e71b33a7 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1960,6 +1960,7 @@ struct kvm_x86_nested_ops { struct kvm_nested_state __user *user_kvm_nested_state, struct kvm_nested_state *kvm_state); bool (*get_nested_state_pages)(struct kvm_vcpu *vcpu); + bool (*is_nested_state_invalid)(struct kvm_vcpu *vcpu); int (*write_log_dirty)(struct kvm_vcpu *vcpu, gpa_t l2_gpa); =20 int (*enable_evmcs)(struct kvm_vcpu *vcpu, diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 0de84b30c41d..627a6c24625d 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3588,6 +3588,11 @@ static bool vmx_get_nested_state_pages(struct kvm_vc= pu *vcpu) return true; } =20 +static bool vmx_is_nested_state_invalid(struct kvm_vcpu *vcpu) +{ + return false; +} + static int nested_vmx_write_pml_buffer(struct kvm_vcpu *vcpu, gpa_t gpa) { struct vmcs12 *vmcs12; @@ -7527,6 +7532,7 @@ struct kvm_x86_nested_ops vmx_nested_ops =3D { .get_state =3D vmx_get_nested_state, .set_state =3D vmx_set_nested_state, .get_nested_state_pages =3D vmx_get_nested_state_pages, + .is_nested_state_invalid =3D vmx_is_nested_state_invalid, .write_log_dirty =3D nested_vmx_write_pml_buffer, #ifdef CONFIG_KVM_HYPERV .enable_evmcs =3D nested_enable_evmcs, diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 4b8138bd4857..1a9c1171df49 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2262,12 +2262,24 @@ int kvm_emulate_monitor(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_emulate_monitor); =20 +static inline bool kvm_invalid_nested_state(struct kvm_vcpu *vcpu) +{ + if (is_guest_mode(vcpu) && + kvm_x86_ops.nested_ops->is_nested_state_invalid && + kvm_x86_ops.nested_ops->is_nested_state_invalid(vcpu)) { + kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu); + return true; + } + return false; +} + static inline bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu) { xfer_to_guest_mode_prepare(); =20 return READ_ONCE(vcpu->mode) =3D=3D EXITING_GUEST_MODE || - kvm_request_pending(vcpu) || xfer_to_guest_mode_work_pending(); + kvm_request_pending(vcpu) || xfer_to_guest_mode_work_pending() || + kvm_invalid_nested_state(vcpu); } =20 static fastpath_t __handle_fastpath_wrmsr(struct kvm_vcpu *vcpu, u32 msr, = u64 data) --=20 2.43.0