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

[QingFeng Hao]

在 2017/7/3 19:48, Cornelia Huck 写道:

On Mon,  3 Jul 2017 09:38:36 +0200
QingFeng Hao <ha...@linux.vnet.ibm.com> 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 <ha...@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
  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().

Thanks and I'll change it just as Christian's comment.

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

--
Regards
QingFeng Hao