linux-kernel - [PATCH v5 1/3] KVM: X86: Save&restore the triple fault request

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Date:   Fri, 18 Mar 2022 15:49:53 +0800
From:   Chenyi Qiang <chenyi.qiang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 1/3] KVM: X86: Save&restore the triple fault request

For the triple fault sythesized by KVM, e.g. the RSM path or
nested_vmx_abort(), if KVM exits to userspace before the request is
serviced, userspace could migrate the VM and lose the triple fault.
Fix this issue by adding a new event KVM_VCPUEVENT_TRIPLE_FAULT in
get/set_vcpu_events() to track the triple fault request.

Signed-off-by: Chenyi Qiang <chenyi.qiang@...el.com>
---
 Documentation/virt/kvm/api.rst  | 6 ++++++
 arch/x86/include/uapi/asm/kvm.h | 1 +
 arch/x86/kvm/x86.c              | 9 ++++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 691ff84444bd..9682b0a438bd 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1146,6 +1146,9 @@ The following bits are defined in the flags field:
   fields contain a valid state. This bit will be set whenever
   KVM_CAP_EXCEPTION_PAYLOAD is enabled.
 
+- KVM_VCPUEVENT_TRIPLE_FAULT may be set to signal that there's a
+  triple fault request waiting to be serviced.
+
 ARM/ARM64:
 ^^^^^^^^^^
 
@@ -1241,6 +1244,9 @@ can be set in the flags field to signal that the
 exception_has_payload, exception_payload, and exception.pending fields
 contain a valid state and shall be written into the VCPU.
 
+KVM_VCPUEVENT_TRIPLE_FAULT can be set in flags field to signal that a
+triple fault request should be made.
+
 ARM/ARM64:
 ^^^^^^^^^^
 
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index bf6e96011dfe..d8ef0d993e86 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -325,6 +325,7 @@ struct kvm_reinject_control {
 #define KVM_VCPUEVENT_VALID_SHADOW	0x00000004
 #define KVM_VCPUEVENT_VALID_SMM		0x00000008
 #define KVM_VCPUEVENT_VALID_PAYLOAD	0x00000010
+#define KVM_VCPUEVENT_TRIPLE_FAULT	0x00000020
 
 /* Interrupt shadow states */
 #define KVM_X86_SHADOW_INT_MOV_SS	0x01
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4fa4d8269e5b..fee402a700df 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4891,6 +4891,9 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 	if (vcpu->kvm->arch.exception_payload_enabled)
 		events->flags |= KVM_VCPUEVENT_VALID_PAYLOAD;
 
+	if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu))
+		events->flags |= KVM_VCPUEVENT_TRIPLE_FAULT;
+
 	memset(&events->reserved, 0, sizeof(events->reserved));
 }
 
@@ -4903,7 +4906,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 			      | KVM_VCPUEVENT_VALID_SIPI_VECTOR
 			      | KVM_VCPUEVENT_VALID_SHADOW
 			      | KVM_VCPUEVENT_VALID_SMM
-			      | KVM_VCPUEVENT_VALID_PAYLOAD))
+			      | KVM_VCPUEVENT_VALID_PAYLOAD
+			      | KVM_VCPUEVENT_TRIPLE_FAULT))
 		return -EINVAL;
 
 	if (events->flags & KVM_VCPUEVENT_VALID_PAYLOAD) {
@@ -4976,6 +4980,9 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 		}
 	}
 
+	if (events->flags & KVM_VCPUEVENT_TRIPLE_FAULT)
+		kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
+
 	kvm_make_request(KVM_REQ_EVENT, vcpu);
 
 	return 0;
-- 
2.17.1