KVM: x86: Replace late check_nested_events() hack with more precise fix

Add an argument to interrupt_allowed and nmi_allowed, to checking if
interrupt injection is blocked.  Use the hook to handle the case where
an interrupt arrives between check_nested_events() and the injection
logic.  Drop the retry of check_nested_events() that hack-a-fixed the
same condition.

Blocking injection is also a bit of a hack, e.g. KVM should do exiting
and non-exiting interrupt processing in a single pass, but it's a more
precise hack.  The old comment is also misleading, e.g. KVM_REQ_EVENT is
purely an optimization, setting it on every run loop (which KVM doesn't
do) should not affect functionality, only performance.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200423022550.15113-13-sean.j.christopherson@intel.com>
[Extend to SVM, add SMI and NMI.  Even though NMI and SMI cannot come
 asynchronously right now, making the fix generic is easy and removes a
 special case. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4426864..efe6199 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1138,8 +1138,8 @@ struct kvm_x86_ops {
        void (*set_nmi)(struct kvm_vcpu *vcpu);
        void (*queue_exception)(struct kvm_vcpu *vcpu);
        void (*cancel_injection)(struct kvm_vcpu *vcpu);
-       bool (*interrupt_allowed)(struct kvm_vcpu *vcpu);
-       bool (*nmi_allowed)(struct kvm_vcpu *vcpu);
+       bool (*interrupt_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
+       bool (*nmi_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
        bool (*get_nmi_mask)(struct kvm_vcpu *vcpu);
        void (*set_nmi_mask)(struct kvm_vcpu *vcpu, bool masked);
        void (*enable_nmi_window)(struct kvm_vcpu *vcpu);
@@ -1237,7 +1237,7 @@ struct kvm_x86_ops {
 
        void (*setup_mce)(struct kvm_vcpu *vcpu);
 
-       bool (*smi_allowed)(struct kvm_vcpu *vcpu);
+       bool (*smi_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
        int (*pre_enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
        int (*pre_leave_smm)(struct kvm_vcpu *vcpu, const char *smstate);
        int (*enable_smi_window)(struct kvm_vcpu *vcpu);

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index fba8bdc..45c6e4b 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3083,13 +3083,17 @@ bool svm_nmi_blocked(struct kvm_vcpu *vcpu)
        return ret;
 }
 
-static bool svm_nmi_allowed(struct kvm_vcpu *vcpu)
+static bool svm_nmi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
        if (svm->nested.nested_run_pending)
                return false;
 
-        return !svm_nmi_blocked(vcpu);
+       /* An NMI must not be injected into L2 if it's supposed to VM-Exit.  */
+       if (for_injection && is_guest_mode(vcpu) && nested_exit_on_nmi(svm))
+               return false;
+
+       return !svm_nmi_blocked(vcpu);
 }
 
 static bool svm_get_nmi_mask(struct kvm_vcpu *vcpu)
@@ -3138,13 +3142,20 @@ bool svm_interrupt_blocked(struct kvm_vcpu *vcpu)
        return (vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK);
 }
 
-static bool svm_interrupt_allowed(struct kvm_vcpu *vcpu)
+static bool svm_interrupt_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
        if (svm->nested.nested_run_pending)
                return false;
 
-        return !svm_interrupt_blocked(vcpu);
+       /*
+        * An IRQ must not be injected into L2 if it's supposed to VM-Exit,
+        * e.g. if the IRQ arrived asynchronously after checking nested events.
+        */
+       if (for_injection && is_guest_mode(vcpu) && nested_exit_on_intr(svm))
+               return false;
+
+       return !svm_interrupt_blocked(vcpu);
 }
 
 static void enable_irq_window(struct kvm_vcpu *vcpu)
@@ -3812,12 +3823,16 @@ bool svm_smi_blocked(struct kvm_vcpu *vcpu)
        return is_smm(vcpu);
 }
 
-static bool svm_smi_allowed(struct kvm_vcpu *vcpu)
+static bool svm_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
        if (svm->nested.nested_run_pending)
                return false;
 
+       /* An SMI must not be injected into L2 if it's supposed to VM-Exit.  */
+       if (for_injection && is_guest_mode(vcpu) && nested_exit_on_smi(svm))
+               return false;
+
        return !svm_smi_blocked(vcpu);
 }
 

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 71cd210..e1f5fc9 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4523,11 +4523,15 @@ bool vmx_nmi_blocked(struct kvm_vcpu *vcpu)
                 GUEST_INTR_STATE_NMI));
 }
 
-static bool vmx_nmi_allowed(struct kvm_vcpu *vcpu)
+static bool vmx_nmi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        if (to_vmx(vcpu)->nested.nested_run_pending)
                return false;
 
+       /* An NMI must not be injected into L2 if it's supposed to VM-Exit.  */
+       if (for_injection && is_guest_mode(vcpu) && nested_exit_on_nmi(vcpu))
+               return false;
+
        return !vmx_nmi_blocked(vcpu);
 }
 
@@ -4541,11 +4545,18 @@ bool vmx_interrupt_blocked(struct kvm_vcpu *vcpu)
                (GUEST_INTR_STATE_STI | GUEST_INTR_STATE_MOV_SS));
 }
 
-static bool vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
+static bool vmx_interrupt_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        if (to_vmx(vcpu)->nested.nested_run_pending)
                return false;
 
+       /*
+        * An IRQ must not be injected into L2 if it's supposed to VM-Exit,
+        * e.g. if the IRQ arrived asynchronously after checking nested events.
+        */
+       if (for_injection && is_guest_mode(vcpu) && nested_exit_on_intr(vcpu))
+               return false;
+
        return !vmx_interrupt_blocked(vcpu);
 }
 
@@ -7688,7 +7699,7 @@ static void vmx_setup_mce(struct kvm_vcpu *vcpu)
                        ~FEAT_CTL_LMCE_ENABLED;
 }
 
-static bool vmx_smi_allowed(struct kvm_vcpu *vcpu)
+static bool vmx_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
        /* we need a nested vmexit to enter SMM, postpone if run is pending */
        if (to_vmx(vcpu)->nested.nested_run_pending)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cb250f1..ec20368 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7766,32 +7766,20 @@ static int inject_pending_event(struct kvm_vcpu *vcpu)
        if (kvm_event_needs_reinjection(vcpu))
                return 0;
 
-       if (vcpu->arch.smi_pending && kvm_x86_ops.smi_allowed(vcpu)) {
+       if (vcpu->arch.smi_pending &&
+           kvm_x86_ops.smi_allowed(vcpu, true)) {
                vcpu->arch.smi_pending = false;
                ++vcpu->arch.smi_count;
                enter_smm(vcpu);
-       } else if (vcpu->arch.nmi_pending && kvm_x86_ops.nmi_allowed(vcpu)) {
+       } else if (vcpu->arch.nmi_pending &&
+                  kvm_x86_ops.nmi_allowed(vcpu, true)) {
                --vcpu->arch.nmi_pending;
                vcpu->arch.nmi_injected = true;
                kvm_x86_ops.set_nmi(vcpu);
-       } else if (kvm_cpu_has_injectable_intr(vcpu)) {
-               /*
-                * Because interrupts can be injected asynchronously, we are
-                * calling check_nested_events again here to avoid a race condition.
-                * See https://lkml.org/lkml/2014/7/2/60 for discussion about this
-                * proposal and current concerns.  Perhaps we should be setting
-                * KVM_REQ_EVENT only on certain events and not unconditionally?
-                */
-               if (is_guest_mode(vcpu)) {
-                       r = kvm_x86_ops.nested_ops->check_events(vcpu);
-                       if (r != 0)
-                               return r;
-               }
-               if (kvm_x86_ops.interrupt_allowed(vcpu)) {
-                       kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu),
-                                           false);
-                       kvm_x86_ops.set_irq(vcpu);
-               }
+       } else if (kvm_cpu_has_injectable_intr(vcpu) &&
+                  kvm_x86_ops.interrupt_allowed(vcpu, true)) {
+               kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu), false);
+               kvm_x86_ops.set_irq(vcpu);
        }
 
        return 0;
@@ -10203,12 +10191,12 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
 
        if (kvm_test_request(KVM_REQ_NMI, vcpu) ||
            (vcpu->arch.nmi_pending &&
-            kvm_x86_ops.nmi_allowed(vcpu)))
+            kvm_x86_ops.nmi_allowed(vcpu, false)))
                return true;
 
        if (kvm_test_request(KVM_REQ_SMI, vcpu) ||
            (vcpu->arch.smi_pending &&
-            kvm_x86_ops.smi_allowed(vcpu)))
+            kvm_x86_ops.smi_allowed(vcpu, false)))
                return true;
 
        if (kvm_arch_interrupt_allowed(vcpu) &&
@@ -10260,7 +10248,7 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 
 int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu)
 {
-       return kvm_x86_ops.interrupt_allowed(vcpu);
+       return kvm_x86_ops.interrupt_allowed(vcpu, false);
 }
 
 unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu)
@@ -10425,7 +10413,7 @@ bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)
         * If interrupts are off we cannot even use an artificial
         * halt state.
         */
-       return kvm_x86_ops.interrupt_allowed(vcpu);
+       return kvm_arch_interrupt_allowed(vcpu);
 }
 
 void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,