Re: [PATCH 2/3] KVM: s390: preserve deliverable_mask in __airqs_kick_single_vcpu

[Claudio Imbrenda]

On Tue, 19 Oct 2021 19:54:00 +0200
Halil Pasic <pasic@xxxxxxxxxxxxx> wrote:

> Changing the deliverable mask in __airqs_kick_single_vcpu() is a bug. If
> one idle vcpu can't take the interrupts we want to deliver, we should
> look for another vcpu that can, instead of saying that we don't want
> to deliver these interrupts by clearing the bits from the
> deliverable_mask.
> 
> Signed-off-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Fixes: 9f30f6216378 ("KVM: s390: add gib_alert_irq_handler()")

Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

> ---
>  arch/s390/kvm/interrupt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 10722455fd02..2245f4b8d362 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -3053,13 +3053,14 @@ static void __airqs_kick_single_vcpu(struct kvm *kvm, u8 deliverable_mask)
>  	int vcpu_idx, online_vcpus = atomic_read(&kvm->online_vcpus);
>  	struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
>  	struct kvm_vcpu *vcpu;
> +	u8 vcpu_isc_mask;
>  
>  	for_each_set_bit(vcpu_idx, kvm->arch.idle_mask, online_vcpus) {
>  		vcpu = kvm_get_vcpu(kvm, vcpu_idx);
>  		if (psw_ioint_disabled(vcpu))
>  			continue;
> -		deliverable_mask &= (u8)(vcpu->arch.sie_block->gcr[6] >> 24);
> -		if (deliverable_mask) {
> +		vcpu_isc_mask = (u8)(vcpu->arch.sie_block->gcr[6] >> 24);
> +		if (deliverable_mask & vcpu_isc_mask) {
>  			/* lately kicked but not yet running */
>  			if (test_and_set_bit(vcpu_idx, gi->kicked_mask))
>  				return;