[PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the injected #PF is async_pf

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From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

Add an nested_apf field to vcpu->arch.exception to identify an async page 
fault, and constructs the expected vm-exit information fields. Force a 
nested VM exit from nested_vmx_check_exception() if the injected #PF is 
async page fault. Extending the userspace interface KVM_GET_VCPU_EVENTS
and KVM_SET_VCPU_EVENTS for live migration.

Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
 Documentation/virtual/kvm/api.txt     |  8 ++++++--
 arch/x86/include/asm/kvm_emulate.h    |  1 +
 arch/x86/include/asm/kvm_host.h       |  2 ++
 arch/x86/include/uapi/asm/kvm.h       |  3 ++-
 arch/x86/kvm/svm.c                    | 16 ++++++++++------
 arch/x86/kvm/vmx.c                    | 17 ++++++++++++++---
 arch/x86/kvm/x86.c                    | 19 +++++++++++++++----
 tools/arch/x86/include/uapi/asm/kvm.h |  3 ++-
 8 files changed, 52 insertions(+), 17 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 4029943..a991a7c 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -832,7 +832,7 @@ struct kvm_vcpu_events {
 		__u8 injected;
 		__u8 nr;
 		__u8 has_error_code;
-		__u8 pad;
+		__u8 nested_apf;
 		__u32 error_code;
 	} exception;
 	struct {
@@ -857,7 +857,7 @@ struct kvm_vcpu_events {
 	} smi;
 };
 
-Only two fields are defined in the flags field:
+Only three fields are defined in the flags field:
 
 - KVM_VCPUEVENT_VALID_SHADOW may be set in the flags field to signal that
   interrupt.shadow contains a valid state.
@@ -865,6 +865,9 @@ Only two fields are defined in the flags field:
 - KVM_VCPUEVENT_VALID_SMM may be set in the flags field to signal that
   smi contains a valid state.
 
+- KVM_VCPUEVENT_VALID_ASYNC_PF may be set in the flags field to signal that
+  the exception is an async page fault.
+
 4.32 KVM_SET_VCPU_EVENTS
 
 Capability: KVM_CAP_VCPU_EVENTS
@@ -887,6 +890,7 @@ suppress overwriting the current in-kernel state. The bits are:
 KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
 KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
 KVM_VCPUEVENT_VALID_SMM         - transfer the smi sub-struct.
+KVM_VCPUEVENT_VALID_ASYNC_PF    - transfer async page fault
 
 If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
 the flags field to signal that interrupt.shadow contains a valid state and
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 722d0e5..fde36f1 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -23,6 +23,7 @@ struct x86_exception {
 	u16 error_code;
 	bool nested_page_fault;
 	u64 address; /* cr2 or nested page fault gpa */
+	u8 async_page_fault;
 };
 
 /*
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e20d8a8..71aef4b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -545,6 +545,7 @@ struct kvm_vcpu_arch {
 		bool reinject;
 		u8 nr;
 		u32 error_code;
+		u8 nested_apf;
 	} exception;
 
 	struct kvm_queued_interrupt {
@@ -646,6 +647,7 @@ struct kvm_vcpu_arch {
 		u32 id;
 		bool send_user_only;
 		u32 host_apf_reason;
+		unsigned long nested_apf_token;
 	} apf;
 
 	/* OSVW MSRs (AMD only) */
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index c2824d0..c9556ec 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -287,6 +287,7 @@ struct kvm_reinject_control {
 #define KVM_VCPUEVENT_VALID_SIPI_VECTOR	0x00000002
 #define KVM_VCPUEVENT_VALID_SHADOW	0x00000004
 #define KVM_VCPUEVENT_VALID_SMM		0x00000008
+#define KVM_VCPUEVENT_VALID_ASYNC_PF 0x00000010
 
 /* Interrupt shadow states */
 #define KVM_X86_SHADOW_INT_MOV_SS	0x01
@@ -298,7 +299,7 @@ struct kvm_vcpu_events {
 		__u8 injected;
 		__u8 nr;
 		__u8 has_error_code;
-		__u8 pad;
+		__u8 nested_apf;
 		__u32 error_code;
 	} exception;
 	struct {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8f263bf..49cdb8e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2367,15 +2367,19 @@ static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 	if (!is_guest_mode(&svm->vcpu))
 		return 0;
 
+	vmexit = nested_svm_intercept(svm);
+	if (vmexit != NESTED_EXIT_DONE)
+		return 0;
+
 	svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + nr;
 	svm->vmcb->control.exit_code_hi = 0;
 	svm->vmcb->control.exit_info_1 = error_code;
-	svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
-
-	vmexit = nested_svm_intercept(svm);
-	if (vmexit == NESTED_EXIT_DONE)
-		svm->nested.exit_required = true;
+	if (svm->vcpu.arch.exception.nested_apf)
+		svm->vmcb->control.exit_info_2 = svm->vcpu.arch.apf.nested_apf_token;
+	else
+		svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
 
+	svm->nested.exit_required = true;
 	return vmexit;
 }
 
@@ -2568,7 +2572,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm)
 			vmexit = NESTED_EXIT_DONE;
 		/* async page fault always cause vmexit */
 		else if ((exit_code == SVM_EXIT_EXCP_BASE + PF_VECTOR) &&
-			 svm->vcpu.arch.apf.host_apf_reason != 0)
+			 svm->vcpu.arch.exception.nested_apf != 0)
 			vmexit = NESTED_EXIT_DONE;
 		break;
 	}
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d20f794..8724ea6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2418,13 +2418,24 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
  * KVM wants to inject page-faults which it got to the guest. This function
  * checks whether in a nested guest, we need to inject them to L1 or L2.
  */
-static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr)
+static int nested_vmx_check_exception(struct kvm_vcpu *vcpu)
 {
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+	unsigned int nr = vcpu->arch.exception.nr;
 
-	if (!(vmcs12->exception_bitmap & (1u << nr)))
+	if (!((vmcs12->exception_bitmap & (1u << nr)) ||
+		(nr == PF_VECTOR && vcpu->arch.exception.nested_apf)))
 		return 0;
 
+	if (vcpu->arch.exception.nested_apf) {
+		vmcs_write32(VM_EXIT_INTR_ERROR_CODE, vcpu->arch.exception.error_code);
+		nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
+			PF_VECTOR | INTR_TYPE_HARD_EXCEPTION |
+			INTR_INFO_DELIVER_CODE_MASK | INTR_INFO_VALID_MASK,
+			vcpu->arch.apf.nested_apf_token);
+		return 1;
+	}
+
 	nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
 			  vmcs_read32(VM_EXIT_INTR_INFO),
 			  vmcs_readl(EXIT_QUALIFICATION));
@@ -2441,7 +2452,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
 	u32 intr_info = nr | INTR_INFO_VALID_MASK;
 
 	if (!reinject && is_guest_mode(vcpu) &&
-	    nested_vmx_check_exception(vcpu, nr))
+	    nested_vmx_check_exception(vcpu))
 		return;
 
 	if (has_error_code) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7511c0a..5756811 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -452,7 +452,12 @@ EXPORT_SYMBOL_GPL(kvm_complete_insn_gp);
 void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault)
 {
 	++vcpu->stat.pf_guest;
-	vcpu->arch.cr2 = fault->address;
+	vcpu->arch.exception.nested_apf =
+		is_guest_mode(vcpu) && fault->async_page_fault;
+	if (vcpu->arch.exception.nested_apf)
+		vcpu->arch.apf.nested_apf_token = fault->address;
+	else
+		vcpu->arch.cr2 = fault->address;
 	kvm_queue_exception_e(vcpu, PF_VECTOR, fault->error_code);
 }
 EXPORT_SYMBOL_GPL(kvm_inject_page_fault);
@@ -3072,7 +3077,7 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 		!kvm_exception_is_soft(vcpu->arch.exception.nr);
 	events->exception.nr = vcpu->arch.exception.nr;
 	events->exception.has_error_code = vcpu->arch.exception.has_error_code;
-	events->exception.pad = 0;
+	events->exception.nested_apf = vcpu->arch.exception.nested_apf;
 	events->exception.error_code = vcpu->arch.exception.error_code;
 
 	events->interrupt.injected =
@@ -3096,7 +3101,8 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 
 	events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
 			 | KVM_VCPUEVENT_VALID_SHADOW
-			 | KVM_VCPUEVENT_VALID_SMM);
+			 | KVM_VCPUEVENT_VALID_SMM
+			 | KVM_VCPUEVENT_VALID_ASYNC_PF);
 	memset(&events->reserved, 0, sizeof(events->reserved));
 }
 
@@ -3108,7 +3114,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 	if (events->flags & ~(KVM_VCPUEVENT_VALID_NMI_PENDING
 			      | KVM_VCPUEVENT_VALID_SIPI_VECTOR
 			      | KVM_VCPUEVENT_VALID_SHADOW
-			      | KVM_VCPUEVENT_VALID_SMM))
+			      | KVM_VCPUEVENT_VALID_SMM
+			      | KVM_VCPUEVENT_VALID_ASYNC_PF))
 		return -EINVAL;
 
 	if (events->exception.injected &&
@@ -3126,6 +3133,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 	vcpu->arch.exception.pending = events->exception.injected;
 	vcpu->arch.exception.nr = events->exception.nr;
 	vcpu->arch.exception.has_error_code = events->exception.has_error_code;
+	if (events->flags & KVM_VCPUEVENT_VALID_ASYNC_PF)
+		vcpu->arch.exception.nested_apf = events->exception.nested_apf;
 	vcpu->arch.exception.error_code = events->exception.error_code;
 
 	vcpu->arch.interrupt.pending = events->interrupt.injected;
@@ -8573,6 +8582,7 @@ void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
 		fault.error_code = 0;
 		fault.nested_page_fault = false;
 		fault.address = work->arch.token;
+		fault.async_page_fault = true;
 		kvm_inject_page_fault(vcpu, &fault);
 	}
 }
@@ -8595,6 +8605,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
 		fault.error_code = 0;
 		fault.nested_page_fault = false;
 		fault.address = work->arch.token;
+		fault.async_page_fault = true;
 		kvm_inject_page_fault(vcpu, &fault);
 	}
 	vcpu->arch.apf.halted = false;
diff --git a/tools/arch/x86/include/uapi/asm/kvm.h b/tools/arch/x86/include/uapi/asm/kvm.h
index c2824d0..c9556ec 100644
--- a/tools/arch/x86/include/uapi/asm/kvm.h
+++ b/tools/arch/x86/include/uapi/asm/kvm.h
@@ -287,6 +287,7 @@ struct kvm_reinject_control {
 #define KVM_VCPUEVENT_VALID_SIPI_VECTOR	0x00000002
 #define KVM_VCPUEVENT_VALID_SHADOW	0x00000004
 #define KVM_VCPUEVENT_VALID_SMM		0x00000008
+#define KVM_VCPUEVENT_VALID_ASYNC_PF 0x00000010
 
 /* Interrupt shadow states */
 #define KVM_X86_SHADOW_INT_MOV_SS	0x01
@@ -298,7 +299,7 @@ struct kvm_vcpu_events {
 		__u8 injected;
 		__u8 nr;
 		__u8 has_error_code;
-		__u8 pad;
+		__u8 nested_apf;
 		__u32 error_code;
 	} exception;
 	struct {
-- 
2.7.4




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