[PATCH v2 3/6] KVM: VMX: Handle vectoring error in check_emulate_instruction

[Ivan Orlov <iorlov@amazon.com>]

Move unhandleable vmexit due to MMIO during vectoring error detection
into check_emulate_instruction. Implement a function which checks if
emul_type indicates MMIO so it can be used for both VMX and SVM.

Fix the comment about EMULTYPE_PF as this flag doesn't necessarily
mean MMIO anymore: it can also be set due to the write protection
violation.

Signed-off-by: Ivan Orlov <iorlov@amazon.com>
---
V1 -> V2:
- Detect the unhandleable vectoring error in vmx_check_emulate_instruction
instead of handling it in the common MMU code (which is specific for
cached MMIO)

 arch/x86/include/asm/kvm_host.h | 10 ++++++++--
 arch/x86/kvm/vmx/vmx.c          | 25 ++++++++++++-------------
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index eb413079b7c6..3de9702a9135 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2017,8 +2017,8 @@ u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
  *			VMware backdoor emulation handles select instructions
  *			and reinjects the #GP for all other cases.
  *
- * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which
- *		 case the CR2/GPA value pass on the stack is valid.
+ * EMULTYPE_PF - Set when an intercepted #PF triggers the emulation, in which case
+ *		 the CR2/GPA value pass on the stack is valid.
  *
  * EMULTYPE_COMPLETE_USER_EXIT - Set when the emulator should update interruptibility
  *				 state and inject single-step #DBs after skipping
@@ -2053,6 +2053,12 @@ u64 vcpu_tsc_khz(struct kvm_vcpu *vcpu);
 #define EMULTYPE_COMPLETE_USER_EXIT (1 << 7)
 #define EMULTYPE_WRITE_PF_TO_SP	    (1 << 8)
 
+static inline bool kvm_is_emul_type_mmio(int emul_type)
+{
+	return (emul_type & EMULTYPE_PF) &&
+		!(emul_type & EMULTYPE_WRITE_PF_TO_SP);
+}
+
 int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
 int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
 					void *insn, int insn_len);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f92740e7e107..a10f35d9704b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1693,6 +1693,8 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data)
 int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
 				  void *insn, int insn_len)
 {
+	bool is_vect;
+
 	/*
 	 * Emulation of instructions in SGX enclaves is impossible as RIP does
 	 * not point at the failing instruction, and even if it did, the code
@@ -1704,6 +1706,13 @@ int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
 		kvm_queue_exception(vcpu, UD_VECTOR);
 		return X86EMUL_PROPAGATE_FAULT;
 	}
+
+	is_vect = to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK;
+
+	/* Emulation is not possible when MMIO happens during event vectoring. */
+	if (kvm_is_emul_type_mmio(emul_type) && is_vect)
+		return X86EMUL_UNHANDLEABLE_VECTORING_IO;
+
 	return X86EMUL_CONTINUE;
 }
 
@@ -6452,7 +6461,6 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	union vmx_exit_reason exit_reason = vmx->exit_reason;
 	u32 vectoring_info = vmx->idt_vectoring_info;
 	u16 exit_handler_index;
-	gpa_t gpa;
 
 	/*
 	 * Flush logged GPAs PML buffer, this will make dirty_bitmap more
@@ -6537,24 +6545,15 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 		return 0;
 	}
 
-	/*
-	 * Note:
-	 * Do not try to fix EXIT_REASON_EPT_MISCONFIG if it caused by
-	 * delivery event since it indicates guest is accessing MMIO.
-	 * The vm-exit can be triggered again after return to guest that
-	 * will cause infinite loop.
-	 */
 	if ((vectoring_info & VECTORING_INFO_VALID_MASK) &&
 	    (exit_reason.basic != EXIT_REASON_EXCEPTION_NMI &&
 	     exit_reason.basic != EXIT_REASON_EPT_VIOLATION &&
 	     exit_reason.basic != EXIT_REASON_PML_FULL &&
 	     exit_reason.basic != EXIT_REASON_APIC_ACCESS &&
 	     exit_reason.basic != EXIT_REASON_TASK_SWITCH &&
-	     exit_reason.basic != EXIT_REASON_NOTIFY)) {
-		gpa = exit_reason.basic == EXIT_REASON_EPT_MISCONFIG
-		      ? vmcs_read64(GUEST_PHYSICAL_ADDRESS) : INVALID_GPA;
-
-		kvm_prepare_event_vectoring_exit(vcpu, gpa);
+	     exit_reason.basic != EXIT_REASON_NOTIFY &&
+	     exit_reason.basic != EXIT_REASON_EPT_MISCONFIG)) {
+		kvm_prepare_event_vectoring_exit(vcpu, INVALID_GPA);
 		return 0;
 	}
 
-- 
2.43.0