On Tue, Jul 27, 2021, Paolo Bonzini wrote:
> Once an exception has been injected, any side effects related to
> the exception (such as setting CR2 or DR6) have been taked place.
> Therefore, once KVM sets the VM-entry interruption information
> field or the AMD EVENTINJ field, the next VM-entry must deliver that
> exception.
>
> Pending interrupts are processed after injected exceptions, so
> in theory it would not be a problem to use KVM_INTERRUPT when
> an injected exception is present. However, DOSEMU is using
> run->ready_for_interrupt_injection to detect interrupt windows
> and then using KVM_SET_SREGS/KVM_SET_REGS to inject the
> interrupt manually. For this to work, the interrupt window
> must be delayed after the completion of the previous event
> injection.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Stas Sergeev <stsp2@xxxxxxxxx>
> Tested-by: Stas Sergeev <stsp2@xxxxxxxxx>
> Fixes: 71cc849b7093 ("KVM: x86: Fix split-irqchip vs interrupt injection window request")
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4116567f3d44..e5d5c5ed7dd4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4358,8 +4358,17 @@ static int kvm_cpu_accept_dm_intr(struct kvm_vcpu *vcpu)
>
> static int kvm_vcpu_ready_for_interrupt_injection(struct kvm_vcpu *vcpu)
> {
> - return kvm_arch_interrupt_allowed(vcpu) &&
> - kvm_cpu_accept_dm_intr(vcpu);
> + /*
> + * Do not cause an interrupt window exit if an exception
> + * is pending or an event needs reinjection; userspace
> + * might want to inject the interrupt manually using KVM_SET_REGS
> + * or KVM_SET_SREGS. For that to work, we must be at an
> + * instruction boundary and with no events half-injected.
> + */
> + return (kvm_arch_interrupt_allowed(vcpu) &&
Ha, adding a '(' is one way to fix the indentation.
Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> + kvm_cpu_accept_dm_intr(vcpu) &&
> + !kvm_event_needs_reinjection(vcpu) &&
> + !vcpu->arch.exception.pending);
> }
>
> static int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
> --
> 2.27.0
>
