On 22 Aug 2023, at 8:38 AM, Raphael Norwitz <raphael.norw...@nutanix.com>
wrote:
On Aug 17, 2023, at 2:40 AM, Li Feng <fen...@smartx.com> wrote:
2023年8月14日 下午8:11，Raphael Norwitz <raphael.norw...@nutanix.com> 写道：
Why can’t we rather fix this by adding a “event_cb” param to
vhost_user_async_close and then call qemu_chr_fe_set_handlers in
vhost_user_async_close_bh()?
Even if calling vhost_dev_cleanup() twice is safe today I worry future
changes may easily stumble over the reconnect case and introduce crashes or
double frees.
I think add a new event_cb is not good enough. ‘qemu_chr_fe_set_handlers’
has been called in vhost_user_async_close, and will be called in event->cb,
so why need add a
new event_cb?
I’m suggesting calling the data->event_cb instead of the data->cb if we hit
the error case where vhost->vdev is NULL. Something like:
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 8dcf049d42..edf1dccd44 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2648,6 +2648,10 @@ typedef struct {
static void vhost_user_async_close_bh(void *opaque)
{
VhostAsyncCallback *data = opaque;
+
+ VirtIODevice *vdev = VIRTIO_DEVICE(data->dev);
+ VHostUserBlk *s = VHOST_USER_BLK(vdev);
+
struct vhost_dev *vhost = data->vhost;
/*
@@ -2657,6 +2661,9 @@ static void vhost_user_async_close_bh(void *opaque)
*/
if (vhost->vdev) {
data->cb(data->dev);
+ } else if (data->event_cb) {
+ qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, data->event_cb,
+ NULL, data->dev, NULL, true);
}
g_free(data);
data->event_cb would be vhost_user_blk_event().
I think that makes the error path a lot easier to reason about and more
future proof.
For avoiding to call the vhost_dev_cleanup() twice, add a ‘inited’ in
struct vhost-dev to mark if it’s inited like this:
This is better than the original, but let me know what you think of my
alternative.
The vhost_user_async_close_bh() is a common function in vhost-user.c, and
vhost_user_async_close() is used by vhost-user-scsi/blk/gpio,
However, in your patch it’s limited to VhostUserBlk, so I think my fix is
more reasonable.
Thanks,
LI
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index e2f6ffb446..edc80c0231 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1502,6 +1502,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void
*opaque,
goto fail_busyloop;
}
+ hdev->inited = true;
return 0;
fail_busyloop:
@@ -1520,6 +1521,10 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
{
int i;
+ if (!hdev->inited) {
+ return;
+ }
+ hdev->inited = false;
trace_vhost_dev_cleanup(hdev);
for (i = 0; i < hdev->nvqs; ++i) {
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index ca3131b1af..74b1aec960 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -123,6 +123,7 @@ struct vhost_dev {
/* @started: is the vhost device started? */
bool started;
bool log_enabled;
+ bool inited;
uint64_t log_size;
Error *migration_blocker;
const VhostOps *vhost_ops;
Thanks.
On Aug 4, 2023, at 1:29 AM, Li Feng <fen...@smartx.com> wrote:
When the vhost-user is reconnecting to the backend, and if the vhost-user
fails
at the get_features in vhost_dev_init(), then the reconnect will fail
and it will not be retriggered forever.
The reason is:
When the vhost-user fail at get_features, the vhost_dev_cleanup will be
called
immediately.
vhost_dev_cleanup calls 'memset(hdev, 0, sizeof(struct vhost_dev))'.
The reconnect path is:
vhost_user_blk_event
vhost_user_async_close(.. vhost_user_blk_disconnect ..)
qemu_chr_fe_set_handlers <----- clear the notifier callback
schedule vhost_user_async_close_bh
The vhost->vdev is null, so the vhost_user_blk_disconnect will not be
called, then the event fd callback will not be reinstalled.
With this patch, the vhost_user_blk_disconnect will call the
vhost_dev_cleanup() again, it's safe.
All vhost-user devices have this issue, including vhost-user-blk/scsi.
Fixes: 71e076a07d ("hw/virtio: generalise CHR_EVENT_CLOSED handling")
Signed-off-by: Li Feng <fen...@smartx.com>
---
hw/virtio/vhost-user.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 8dcf049d42..697b403fe2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2648,16 +2648,8 @@ typedef struct {
static void vhost_user_async_close_bh(void *opaque)
{
VhostAsyncCallback *data = opaque;
- struct vhost_dev *vhost = data->vhost;
- /*
- * If the vhost_dev has been cleared in the meantime there is
- * nothing left to do as some other path has completed the
- * cleanup.
- */
- if (vhost->vdev) {
- data->cb(data->dev);
- }
+ data->cb(data->dev);
g_free(data);
}
--
2.41.0
