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

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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>
This commit is contained in:
Paolo Bonzini 2020-04-23 14:08:58 -04:00
parent 7ab0abdb55
commit c300ab9f08
4 changed files with 49 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/include/asm/kvm_host.h
View File

@ -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);

25
arch/x86/kvm/svm/svm.c
View File

@ -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);
}

17
arch/x86/kvm/vmx/vmx.c
View File

@ -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)

36
arch/x86/kvm/x86.c
View File

@ -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,