linux-kernel - Re: [PATCH 2/3] KVM: s390: preserve deliverable_mask in __airqs_kick_single

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Date:   Wed, 20 Oct 2021 10:08:48 +0200
From:   Michael Mueller <mimu@...ux.ibm.com>
To:     Halil Pasic <pasic@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>, farman@...ux.ibm.com,
        kvm@...r.kernel.org
Subject: Re: [PATCH 2/3] KVM: s390: preserve deliverable_mask in
 __airqs_kick_single_vcpu



On 19.10.21 19:54, Halil Pasic 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@...ux.ibm.com>
> Fixes: 9f30f6216378 ("KVM: s390: add gib_alert_irq_handler()")

Reviewed-by: Michael Mueller <mimu@...ux.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;
>