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KVM: nVMX: Unconditionally purge queued/injected events on nested "exit"

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Drop pending exceptions and events queued for re-injection when leaving
nested guest mode, even if the "exit" is due to VM-Fail, SMI, or forced
by host userspace.  Failure to purge events could result in an event
belonging to L2 being injected into L1.

This _should_ never happen for VM-Fail as all events should be blocked by
nested_run_pending, but it's possible if KVM, not the L1 hypervisor, is
the source of VM-Fail when running vmcs02.

SMI is a nop (barring unknown bugs) as recognition of SMI and thus entry
to SMM is blocked by pending exceptions and re-injected events.

Forced exit is definitely buggy, but has likely gone unnoticed because
userspace probably follows the forced exit with KVM_SET_VCPU_EVENTS (or
some other ioctl() that purges the queue).

Fixes: 4f350c6dbc ("kvm: nVMX: Handle deferred early VMLAUNCH/VMRESUME failure properly")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-2-seanjc@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-08-30 23:15:48 +00:00 committed by Paolo Bonzini
parent 794663e13f
commit d953540430
1 changed files with 11 additions and 8 deletions
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19
arch/x86/kvm/vmx/nested.c
View file

@ -4301,14 +4301,6 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
nested_vmx_abort(vcpu,
VMX_ABORT_SAVE_GUEST_MSR_FAIL);
}
/*
* Drop what we picked up for L2 via vmx_complete_interrupts. It is
* preserved above and would only end up incorrectly in L1.
*/
vcpu->arch.nmi_injected = false;
kvm_clear_exception_queue(vcpu);
kvm_clear_interrupt_queue(vcpu);
}
/*
@ -4648,6 +4640,17 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
WARN_ON_ONCE(nested_early_check);
}
/*
* Drop events/exceptions that were queued for re-injection to L2
* (picked up via vmx_complete_interrupts()), as well as exceptions
* that were pending for L2. Note, this must NOT be hoisted above
* prepare_vmcs12(), events/exceptions queued for re-injection need to
* be captured in vmcs12 (see vmcs12_save_pending_event()).
*/
vcpu->arch.nmi_injected = false;
kvm_clear_exception_queue(vcpu);
kvm_clear_interrupt_queue(vcpu);
vmx_switch_vmcs(vcpu, &vmx->vmcs01);
/* Update any VMCS fields that might have changed while L2 ran */