> On 22 Aug 2023, at 6:17 PM, Raphael Norwitz <raphael.norw...@nutanix.com>
> wrote:
>
>
>
>> 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.
OK, I will change it in V2.
>
>>
>> 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
