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

Claudio Imbrenda
2021-10-20T05:43:43Z

On Tue, 19 Oct 2021 19:54:00 +0200
Halil Pasic <pasic@linux.ibm.com> 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@linux.ibm.com>
> Fixes: 9f30f6216378 ("KVM: s390: add gib_alert_irq_handler()")

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
> 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;