[PATCH] KVM: arm64: Only open the interrupt window on exit due to an interrupt

[Mark Rutland]

On Fri, Mar 04, 2022 at 01:59:14PM +0000, Marc Zyngier wrote:
> Now that we properly account for interrupts taken whilst the guest
> was running, it becomes obvious that there is no need to open
> this accounting window if we didn't exit because of an interrupt.
> 
> This saves a number of system register accesses and other barriers
> if we exited for any other reason (such as a trap, for example).
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>

Acked-by: Mark Rutland <mark.rutland at arm.com>

Mark.

> ---
>  arch/arm64/kvm/arm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index fefd5774ab55..f49ebdd9c990 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -887,9 +887,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>  		 * context synchronization event) is necessary to ensure that
>  		 * pending interrupts are taken.
>  		 */
> -		local_irq_enable();
> -		isb();
> -		local_irq_disable();
> +		if (ARM_EXCEPTION_CODE(ret) == ARM_EXCEPTION_IRQ) {
> +			local_irq_enable();
> +			isb();
> +			local_irq_disable();
> +		}
>  
>  		guest_timing_exit_irqoff();
>  
> -- 
> 2.34.1
>