KVM: Non-atomic interrupt injection

Change the interrupt injection code to work from preemptible, interrupts
enabled context.  This works by adding a ->cancel_injection() operation
that undoes an injection in case we were not able to actually enter the guest
(this condition could never happen with atomic injection).

Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 40 insertions, 20 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b43686a44877..80224bf5d4f8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -552,6 +552,7 @@ struct kvm_x86_ops {
         void (*queue_exception)(struct kvm_vcpu *vcpu, unsigned nr,
                                 bool has_error_code, u32 error_code,
                                 bool reinject);
+        void (*cancel_injection)(struct kvm_vcpu *vcpu);
         int (*interrupt_allowed)(struct kvm_vcpu *vcpu);
         int (*nmi_allowed)(struct kvm_vcpu *vcpu);
         bool (*get_nmi_mask)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1d2ea65d3537..1a85fc507cf7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3261,6 +3261,17 @@ static void svm_complete_interrupts(struct vcpu_svm *svm)
         }
 }
 
+static void svm_cancel_injection(struct kvm_vcpu *vcpu)
+{
+        struct vcpu_svm *svm = to_svm(vcpu);
+        struct vmcb_control_area *control = &svm->vmcb->control;
+
+        control->exit_int_info = control->event_inj;
+        control->exit_int_info_err = control->event_inj_err;
+        control->event_inj = 0;
+        svm_complete_interrupts(svm);
+}
+
 #ifdef CONFIG_X86_64
 #define R "r"
 #else
@@ -3631,6 +3642,7 @@ static struct kvm_x86_ops svm_x86_ops = {
         .set_irq = svm_set_irq,
         .set_nmi = svm_inject_nmi,
         .queue_exception = svm_queue_exception,
+        .cancel_injection = svm_cancel_injection,
         .interrupt_allowed = svm_interrupt_allowed,
         .nmi_allowed = svm_nmi_allowed,
         .get_nmi_mask = svm_get_nmi_mask,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3237f6cc930d..70af3db372d7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3895,6 +3895,16 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
                                   IDT_VECTORING_ERROR_CODE);
 }
 
+static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
+{
+        __vmx_complete_interrupts(to_vmx(vcpu),
+                                  vmcs_read32(VM_ENTRY_INTR_INFO_FIELD),
+                                  VM_ENTRY_INSTRUCTION_LEN,
+                                  VM_ENTRY_EXCEPTION_ERROR_CODE);
+
+        vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);
+}
+
 /*
  * Failure to inject an interrupt should give us the information
  * in IDT_VECTORING_INFO_FIELD.  However, if the failure occurs
@@ -4348,6 +4358,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
         .set_irq = vmx_inject_irq,
         .set_nmi = vmx_inject_nmi,
         .queue_exception = vmx_queue_exception,
+        .cancel_injection = vmx_cancel_injection,
         .interrupt_allowed = vmx_interrupt_allowed,
         .nmi_allowed = vmx_nmi_allowed,
         .get_nmi_mask = vmx_get_nmi_mask,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e7198036db61..a465bd29f381 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5005,7 +5005,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
         int r;
         bool req_int_win = !irqchip_in_kernel(vcpu->kvm) &&
                 vcpu->run->request_interrupt_window;
-        bool req_event;
 
         if (vcpu->requests) {
                 if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
@@ -5041,6 +5040,21 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
         if (unlikely(r))
                 goto out;
 
+        if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
+                inject_pending_event(vcpu);
+
+                /* enable NMI/IRQ window open exits if needed */
+                if (vcpu->arch.nmi_pending)
+                        kvm_x86_ops->enable_nmi_window(vcpu);
+                else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
+                        kvm_x86_ops->enable_irq_window(vcpu);
+
+                if (kvm_lapic_enabled(vcpu)) {
+                        update_cr8_intercept(vcpu);
+                        kvm_lapic_sync_to_vapic(vcpu);
+                }
+        }
+
         preempt_disable();
 
         kvm_x86_ops->prepare_guest_switch(vcpu);
@@ -5053,35 +5067,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
         local_irq_disable();
 
-        req_event = kvm_check_request(KVM_REQ_EVENT, vcpu);
-
         if (!atomic_read(&vcpu->guest_mode) || vcpu->requests
             || need_resched() || signal_pending(current)) {
-                if (req_event)
-                        kvm_make_request(KVM_REQ_EVENT, vcpu);
                 atomic_set(&vcpu->guest_mode, 0);
                 smp_wmb();
                 local_irq_enable();
                 preempt_enable();
+                kvm_x86_ops->cancel_injection(vcpu);
                 r = 1;
                 goto out;
         }
 
-        if (req_event || req_int_win) {
-                inject_pending_event(vcpu);
-
-                /* enable NMI/IRQ window open exits if needed */
-                if (vcpu->arch.nmi_pending)
-                        kvm_x86_ops->enable_nmi_window(vcpu);
-                else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
-                        kvm_x86_ops->enable_irq_window(vcpu);
-
-                if (kvm_lapic_enabled(vcpu)) {
-                        update_cr8_intercept(vcpu);
-                        kvm_lapic_sync_to_vapic(vcpu);
-                }
-        }
-
         srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
 
         kvm_guest_enter();