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Re: [Qemu-block] [Qemu-devel] [PATCH v2 1/1] virtio-scsi-ccw: use ioeven
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v2 1/1] virtio-scsi-ccw: use ioeventfd even when KVM is disabled |
Date: |
Mon, 3 Jul 2017 13:56:04 +0200 |
On Mon, 3 Jul 2017 12:20:03 +0200
Christian Borntraeger <address@hidden> wrote:
> On 07/03/2017 10:51 AM, QingFeng Hao wrote:
>
> > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> > index a3d00196f4..c37f9c3b9e 100644
> > --- a/target/s390x/kvm.c
> > +++ b/target/s390x/kvm.c
> > @@ -2220,6 +2220,9 @@ int kvm_s390_assign_subch_ioeventfd(EventNotifier
> > *notifier, uint32_t sch,
> > .addr = sch,
> > .len = 8,
> > };
> > + if (!kvm_enabled()) {
> > + return 0;
> > + }
>
> thinking more about it. wouldnt it be better to do something like this instead
>
> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> index 058ddad..cc47831 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -1240,7 +1240,11 @@ static inline int
> s390_assign_subch_ioeventfd(EventNotifier *notifier,
> uint32_t sch_id, int vq,
> bool assign)
> {
> - return kvm_s390_assign_subch_ioeventfd(notifier, sch_id, vq, assign);
> + if (kvm_enabled()) {
> + return kvm_s390_assign_subch_ioeventfd(notifier, sch_id, vq, assign);
> + } else {
> + return 0;
> + }
> }
>
> static inline void s390_crypto_reset(void)
Agreed.
>
>
> FWIW, it seems that we (s390) do not have a functional equivalent function as
> commit
> 8c56c1a592b5092d91da8d8943c17777d6462a6f ("memory: emulate ioeventfd") , so
> we will
> not use the iothreads.
Should not be a problem, I think. We may want to cook up an equivalent,
though.
>
>
> > if (!kvm_check_extension(kvm_state, KVM_CAP_IOEVENTFD)) {
> > return -ENOSYS;
> > }
> >
>
>