Re: [Qemu-block] [Qemu-devel] [PATCH v2 1/1] virtio-scsi-ccw: use ioeventfd even when KVM is disabled

[QingFeng Hao]

在 2017/7/4 15:06, Christian Borntraeger 写道:
> On 07/04/2017 05:41 AM, QingFeng Hao wrote:
> > 在 2017/7/3 18:20, Christian Borntraeger 写道:
> > > On 07/03/2017 10:51 AM, QingFeng Hao wrote:
> > > > This patch is based on a similar patch from Stefan Hajnoczi -
> > > > commit c324fd0a39c (" virtio-pci: use ioeventfd even when KVM is disabled)
> > > >
> > > > 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>
> > > > ---
> > > >    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;
> > > > +    }
> > > 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;
> > > +    }
> > >    }
> > Thanks. It makes sense. I'll change it.
> > >    static inline void s390_crypto_reset(void)
> > >
> > >
> > > 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.
> > Ok, but might s390 have skipped the iothread arguments and passed the test, so 
> > we could
> > still keep this test case?
> Yes, lets just fix the test case. We can implement emulated ioeventfds later.
Fine, thanks!
>

--
Regards
QingFeng Hao