[Qemu-devel] [PATCH 7/7] virtio-scsi-ccw: use ioeventfd even when KVM is disabled

[Christian Borntraeger <borntraeger@de.ibm.com>]

From: QingFeng Hao <haoqf@linux.vnet.ibm.com>

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.
Currently we don't have an equivalent to "memory: emulate ioeventfd"
for ccw yet, but that this doesn't hurt and qemu-iotests 068 can pass with
skipping iothread arguments.

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>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20170704132350.11874-2-haoqf@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.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 f0e7fc8..e18fd26 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -789,7 +789,7 @@ 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 9faca04..bdb9bdb 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)
-- 
2.7.4