[v3,1/1] virtio-scsi-ccw: use ioeventfd even when KVM is disabled

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 <haoqf@linux.vnet.ibm.com>
---
 hw/s390x/virtio-ccw.c | 2 +-
 target/s390x/cpu.h    | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

On Tue,  4 Jul 2017 10:32:31 +0200
QingFeng Hao <haoqf@linux.vnet.ibm.com> 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.

It might be good to add a sentence that we don't have an equivalent to
"memory: emulate ioeventfd" for ccw yet, but that this doesn't hurt.

> 
> 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 <haoqf@linux.vnet.ibm.com>
> ---
>  hw/s390x/virtio-ccw.c | 2 +-
>  target/s390x/cpu.h    | 6 +++++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> 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/cpu.h b/target/s390x/cpu.h
> index 9faca04b52..bdb9bdbc9d 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -1264,7 +1264,11 @@ 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)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

在 2017/7/4 17:34, Cornelia Huck 写道:
> On Tue,  4 Jul 2017 10:32:31 +0200
> QingFeng Hao <haoqf@linux.vnet.ibm.com> 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.
> It might be good to add a sentence that we don't have an equivalent to
> "memory: emulate ioeventfd" for ccw yet, but that this doesn't hurt.
Ok, I'll add it. thanks.
>
>> 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 <haoqf@linux.vnet.ibm.com>
>> ---
>>   hw/s390x/virtio-ccw.c | 2 +-
>>   target/s390x/cpu.h    | 6 +++++-
>>   2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> 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/cpu.h b/target/s390x/cpu.h
>> index 9faca04b52..bdb9bdbc9d 100644
>> --- a/target/s390x/cpu.h
>> +++ b/target/s390x/cpu.h
>> @@ -1264,7 +1264,11 @@ 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)
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Thanks!
>