linux-kernel - Re: [PATCH v5 12/15] KVM: s390: do not restore IAM immediately before SIE entry

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Date:   Thu, 3 Jan 2019 16:00:36 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Michael Mueller <mimu@...ux.ibm.com>,
        KVM Mailing List <kvm@...r.kernel.org>
Cc:     Linux-S390 Mailing List <linux-s390@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        kvm390-list@...maker.boeblingen.de.ibm.com,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>
Subject: Re: [PATCH v5 12/15] KVM: s390: do not restore IAM immediately before
 SIE entry

On 19/12/2018 20:17, Michael Mueller wrote:
> The IAM shall no be restored when deliverable interruptions are
> delivered to vcpus by means of the PSW swap mechanism. That would
> trigger the GIB alert millicode although we know that SIE will be
> able to handle the pending interruption on entry.
> 
> Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
> ---
>   arch/s390/kvm/interrupt.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 8307717e3caf..48a93f5e5333 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -328,11 +328,11 @@ static unsigned long disable_iscs(struct kvm_vcpu *vcpu,
>   	return active_mask;
>   }
>   
> -static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu)
> +static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu, u16 irq_flags)
>   {
>   	unsigned long active_mask;
>   
> -	active_mask = pending_irqs(vcpu, IRQ_MASK_ALL);
> +	active_mask = pending_irqs(vcpu, irq_flags);
>   	if (!active_mask)
>   		return 0;
>   
> @@ -1090,7 +1090,7 @@ int kvm_s390_ext_call_pending(struct kvm_vcpu *vcpu)
>   
>   int kvm_s390_vcpu_has_irq(struct kvm_vcpu *vcpu, int exclude_stop)
>   {
> -	if (deliverable_irqs(vcpu))
> +	if (deliverable_irqs(vcpu, IRQ_MASK_ALL | IRQ_FLAG_IAM))

Why do we need to restore IAM here?



-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany