> On Aug 22, 2023, at 12:49 AM, Li Feng <fen...@smartx.com> wrote:
>
>
>
>> 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.
I did not write out the full patch.
vhost-user-scsi/blk/gpio would each provide their own ->event_cb, just like
they each provide a different ->cb today. Looking at it again, data has the
chardev, so no need to use VIRTO_DEVICE() or VHOST_USER_BLK().
The fix generalizes to all device types.
>
> 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
