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Subject: Re: [PATCH 2/3] KVM: s390: preserve deliverable_mask in
 __airqs_kick_single_vcpu
To:     Halil Pasic <pasic@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Michael Mueller <mimu@linux.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     David Hildenbrand <david@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>,
        Tony Krowiak <akrowiak@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Niklas Schnelle <schnelle@linux.ibm.com>, farman@linux.ibm.com,
        kvm@vger.kernel.org
References: <20211019175401.3757927-1-pasic@linux.ibm.com>
 <20211019175401.3757927-3-pasic@linux.ibm.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <e8faa255-5157-4afb-b79f-710c961ef159@de.ibm.com>
Date:   Tue, 19 Oct 2021 23:24:34 +0200
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Am 19.10.21 um 19:54 schrieb Halil Pasic:
> 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: Christian Borntraeger <borntraeger@de.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;
>