[PATCH v2 1/3] KVM: x86: Add a helper to prepare vcpu->run for a SHUTDOWN exit to userspace

[Sean Christopherson <seanjc@google.com>]

Add kvm_prepare_shutdown_exit() to dedup the paths that exit to userspace
with KVM_EXIT_SHUTDOWN, all of which happen to be x86 (presumably other
architectures use KVM_EXIT_SYSTEM_EVENT?).

Note, this adds a clearing of mmio_needed for SVM's shutdown_interception().
Not clearing mmio_needed in that case is all but guaranteed to be benign;
KVM should never enter the guest with outstanding emulated MMIO operations
(the equivalent VMX and TDX paths likely copy+pasted the code from
KVM_REQ_TRIPLE_FAULT, which does need to clear mmio_needed as KVM can
synthesize a triple fault shutdown in the middle of instruction emulation).

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c   | 3 +--
 arch/x86/kvm/vmx/tdx.c   | 3 +--
 arch/x86/kvm/vmx/vmx.c   | 3 +--
 arch/x86/kvm/x86.c       | 3 +--
 include/linux/kvm_host.h | 8 ++++++++
 5 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 0eb1623052c1..d2feb57d774f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2190,7 +2190,6 @@ static int mc_interception(struct kvm_vcpu *vcpu)
 
 static int shutdown_interception(struct kvm_vcpu *vcpu)
 {
-	struct kvm_run *kvm_run = vcpu->run;
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 
@@ -2214,7 +2213,7 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
 		kvm_vcpu_reset(vcpu, true);
 	}
 
-	kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
+	kvm_prepare_shutdown_exit(vcpu);
 	return 0;
 }
 
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index ee1d412b0ee6..29d4751f37fb 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2092,8 +2092,7 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 
 	switch (exit_reason.basic) {
 	case EXIT_REASON_TRIPLE_FAULT:
-		vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
-		vcpu->mmio_needed = 0;
+		kvm_prepare_shutdown_exit(vcpu);
 		return 0;
 	case EXIT_REASON_EXCEPTION_NMI:
 		return tdx_handle_exception_nmi(vcpu);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index dc635145eeaf..35db7197c586 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5588,8 +5588,7 @@ static __always_inline int handle_external_interrupt(struct kvm_vcpu *vcpu)
 
 static int handle_triple_fault(struct kvm_vcpu *vcpu)
 {
-	vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
-	vcpu->mmio_needed = 0;
+	kvm_prepare_shutdown_exit(vcpu);
 	return 0;
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf3fcdfd8ad2..cffd1b6ef789 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8139,8 +8139,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 				kvm_nested_call(triple_fault)(vcpu);
 
 			if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
-				vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
-				vcpu->mmio_needed = 0;
+				kvm_prepare_shutdown_exit(vcpu);
 				r = 0;
 				goto out;
 			}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a836756baebb..02ca5d5d83b5 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2522,6 +2522,14 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
 /* Max number of entries allowed for each kvm dirty ring */
 #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
 
+static inline void kvm_prepare_shutdown_exit(struct kvm_vcpu *vcpu)
+{
+	vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
+#ifdef CONFIG_HAS_IOMEM
+	vcpu->mmio_needed = 0;
+#endif
+}
+
 static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 						 gpa_t gpa, gpa_t size,
 						 bool is_write, bool is_exec,
-- 
2.56.0.rc1.315.gc6ed9934b7-goog