[PATCH 3/3] VMX: Enhance invalid guest state emulation

[Mohammed Gamal <m.gamal005@xxxxxxxxx>]

- Change returned handle_invalid_guest_state() to return relevant exit codes
- Move triggering the emulation from vmx_vcpu_run() to vmx_handle_exit()
- Return to userspace instead of repeatedly trying to emulate
instructions that have already failed

Signed-off-by: Mohammed Gamal <m.gamal005@xxxxxxxxx>
---
 arch/x86/kvm/vmx.c |   24 ++++++++++++++----------
 1 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 78101dd..e422470 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3318,10 +3318,11 @@ static int handle_nmi_window(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
-static void handle_invalid_guest_state(struct kvm_vcpu *vcpu)
+static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	enum emulation_result err = EMULATE_DONE;
+	int ret = 1;
 
 	local_irq_enable();
 	preempt_enable();
@@ -3329,11 +3330,16 @@ static void handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 	while (!guest_state_valid(vcpu)) {
 		err = emulate_instruction(vcpu, 0, 0, 0);
 
-		if (err == EMULATE_DO_MMIO)
+		if (err == EMULATE_DO_MMIO) {
+			ret = 0;
 			break;
+		}
 
 		if (err != EMULATE_DONE) {
 			kvm_report_emulation_failure(vcpu, "emulation failure");
+			vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+			vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+			ret = 0;
 			break;
 		}
 
@@ -3347,6 +3353,7 @@ static void handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 	local_irq_disable();
 
 	vmx->invalid_state_emulation_result = err;
+	return ret;
 }
 
 /*
@@ -3405,9 +3412,12 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
 	/* If we need to emulate an MMIO from handle_invalid_guest_state
 	 * we just return 0 */
 	if (vmx->emulation_required && emulate_invalid_guest_state) {
-		if (guest_state_valid(vcpu))
+		if (guest_state_valid(vcpu)) {
 			vmx->emulation_required = 0;
-		return vmx->invalid_state_emulation_result != EMULATE_DO_MMIO;
+			return vmx->invalid_state_emulation_result != EMULATE_DO_MMIO;	
+		} else {
+			return handle_invalid_guest_state(vcpu);
+		}
 	}
 
 	/* Access CR3 don't cause VMExit in paging mode, so we need
@@ -3603,12 +3613,6 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
 		vmx->entry_time = ktime_get();
 
-	/* Handle invalid guest state instead of entering VMX */
-	if (vmx->emulation_required && emulate_invalid_guest_state) {
-		handle_invalid_guest_state(vcpu);
-		return;
-	}
-
 	if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))
 		vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);
 	if (test_bit(VCPU_REGS_RIP, (unsigned long *)&vcpu->arch.regs_dirty))
-- 
1.6.0.4

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