KVM: VMX: Enhance invalid guest state emulation

- 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@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 20 insertions, 24 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4635298d000..73cb5dd960c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -107,7 +107,6 @@ struct vcpu_vmx {
         } rmode;
         int vpid;
         bool emulation_required;
-        enum emulation_result invalid_state_emulation_result;
 
         /* Support for vnmi-less CPUs */
         int soft_vnmi_blocked;
@@ -3322,35 +3321,37 @@ 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;
-
-        local_irq_enable();
-        preempt_enable();
+        int ret = 1;
 
         while (!guest_state_valid(vcpu)) {
                 err = emulate_instruction(vcpu, 0, 0, 0);
 
-                if (err == EMULATE_DO_MMIO)
-                        break;
+                if (err == EMULATE_DO_MMIO) {
+                        ret = 0;
+                        goto out;
+                }
 
                 if (err != EMULATE_DONE) {
                         kvm_report_emulation_failure(vcpu, "emulation failure");
-                        break;
+                        vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+                        vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+                        ret = 0;
+                        goto out;
                 }
 
                 if (signal_pending(current))
-                        break;
+                        goto out;
                 if (need_resched())
                         schedule();
         }
 
-        preempt_disable();
-        local_irq_disable();
-
-        vmx->invalid_state_emulation_result = err;
+        vmx->emulation_required = 0;
+out:
+        return ret;
 }
 
 /*
@@ -3406,13 +3407,9 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
 
         trace_kvm_exit(exit_reason, kvm_rip_read(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))
-                        vmx->emulation_required = 0;
-                return vmx->invalid_state_emulation_result != EMULATE_DO_MMIO;
-        }
+        /* If guest state is invalid, start emulating */
+        if (vmx->emulation_required && emulate_invalid_guest_state)
+                return handle_invalid_guest_state(vcpu);
 
         /* Access CR3 don't cause VMExit in paging mode, so we need
          * to sync with guest real CR3. */
@@ -3607,11 +3604,10 @@ 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);
+        /* Don't enter VMX if guest state is invalid, let the exit handler
+           start emulation until we arrive back to a valid state */
+        if (vmx->emulation_required && emulate_invalid_guest_state)
                 return;
-        }
 
         if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))
                 vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);