From: Stefan Hajnoczi <stefa...@redhat.com>
This patch is part of an effort to remove the aio_disable_external()
API because it does not fit in a multi-queue block layer world where
many AioContexts may be submitting requests to the same disk.
The SCSI emulation code is already in good shape to stop using
aio_disable_external(). It was only used by commit 9c5aad84da1c
("virtio-scsi: fixed virtio_scsi_ctx_check failed when detaching scsi
disk") to ensure that virtio_scsi_hotunplug() works while the guest
driver is submitting I/O.
Ensure virtio_scsi_hotunplug() is safe as follows:
1. qdev_simple_device_unplug_cb() -> qdev_unrealize() ->
device_set_realized() calls qatomic_set(&dev->realized, false) so
that future scsi_device_get() calls return NULL because they exclude
SCSIDevices with realized=false.
That means virtio-scsi will reject new I/O requests to this
SCSIDevice with VIRTIO_SCSI_S_BAD_TARGET even while
virtio_scsi_hotunplug() is still executing. We are protected against
new requests!
2. scsi_qdev_unrealize() already contains a call to
scsi_device_purge_requests() so that in-flight requests are cancelled
synchronously. This ensures that no in-flight requests remain once
qdev_simple_device_unplug_cb() returns.
Thanks to these two conditions we don't need aio_disable_external()
anymore.
Cc: Zhengui Li <lizhen...@huawei.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Reviewed-by: Daniil Tatianin <d-tatia...@yandex-team.ru>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Kevin Wolf <kw...@redhat.com>
Message-Id: <20230516190238.8401-5-stefa...@redhat.com>
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
hw/scsi/virtio-scsi.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index ae314af3de..c1a7ea9ae2 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -1091,7 +1091,6 @@ static void virtio_scsi_hotunplug(HotplugHandler
*hotplug_dev, DeviceState *dev,
VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
VirtIOSCSI *s = VIRTIO_SCSI(vdev);
SCSIDevice *sd = SCSI_DEVICE(dev);
- AioContext *ctx = s->ctx ?: qemu_get_aio_context();
VirtIOSCSIEventInfo info = {
.event = VIRTIO_SCSI_T_TRANSPORT_RESET,
.reason = VIRTIO_SCSI_EVT_RESET_REMOVED,
@@ -1101,9 +1100,7 @@ static void virtio_scsi_hotunplug(HotplugHandler
*hotplug_dev, DeviceState *dev,
},
};
- aio_disable_external(ctx);
qdev_simple_device_unplug_cb(hotplug_dev, dev, errp);
- aio_enable_external(ctx);
if (s->ctx) {
virtio_scsi_acquire(s);
--
2.40.1
