Re: [Qemu-devel] [PATCH 1/1] virtio-scsi-ccw: use ioeventfd even when KVM is disabled

[Cornelia Huck]

On Mon,  3 Jul 2017 09:38:36 +0200
QingFeng Hao <address@hidden> wrote:

> Do not check kvm_eventfds_enabled() when KVM is disabled since it
> always returns 0.  Since commit
> 8c56c1a592b5092d91da8d8943c17777d6462a6f ("memory: emulate
> ioeventfd") it has been possible to use ioeventfds in qtest or TCG
> mode.
> 
> This patch makes -device virtio-scsi-ccw,iothread=iothread0 work even
> when KVM is disabled.
> 
> I have tested that virtio-scsi-ccw works under tcg both with and
> without iothread.
> 
> This patch fixes qemu-iotests 068, which was accidentally merged early
> despite the dependency on ioeventfd.
> 
> Signed-off-by: QingFeng Hao <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  hw/s390x/virtio-ccw.c | 2 +-
>  target/s390x/kvm.c    | 3 +++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index 90d37cb9ff..35896eb007 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -711,7 +711,7 @@ static void
> virtio_ccw_device_realize(VirtioCcwDevice *dev, Error **errp)
> sch->cssid, sch->ssid, sch->schid, sch->devno, ccw_dev->devno.valid ?
> "user-configured" : "auto-configured"); 
> -    if (!kvm_eventfds_enabled()) {
> +    if (kvm_enabled() && !kvm_eventfds_enabled()) {
>          dev->flags &= ~VIRTIO_CCW_FLAG_USE_IOEVENTFD;
>      }
>  
> 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;
> +    }

I'd prefer if you moved the kvm_enabled() check into
s390_assign_subch_ioeventfd().

>      if (!kvm_check_extension(kvm_state, KVM_CAP_IOEVENTFD)) {
>          return -ENOSYS;
>      }