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Re: [Qemu-block] [Qemu-devel] [PATCH v2 1/1] virtio-scsi-ccw: use ioeven
From: |
Christian Borntraeger |
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 12:20:03 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
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;
+ }
}
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.
> if (!kvm_check_extension(kvm_state, KVM_CAP_IOEVENTFD)) {
> return -ENOSYS;
> }
>