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>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4635298d000a2240f35d520c89081572dba79879..73cb5dd960cf5073ea1c56dd803cd544c8ca5ca4 100644 (file)
--- 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]);