On 1/16/2024 1:57 PM, Eugenio Perez Martin wrote:
> On Wed, Jan 10, 2024 at 9:40 PM Steve Sistare <steven.sistare@xxxxxxxxxx> wrote:
>>
>> To pass ownership of a live vdpa device to a new process, the user
>> suspends the device, calls VHOST_NEW_OWNER to change the mm, and calls
>> VHOST_IOTLB_REMAP to change the user virtual addresses to match the new
>> mm. Flush workers in suspend to guarantee that no worker sees the new
>> mm and old VA in between.
>
> The worker should already be stopped by the end of the suspend ioctl,
> so maybe we can consider this a fix?
Do you mean: the current behavior is a bug, independently of my new use case,
so I should submit this patch as a separate bug fix? If yes, then will do.
>> Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
>> ---
>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> index 6304cb0b4770..8734834983cb 100644
>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> @@ -74,6 +74,17 @@ static void vdpasim_worker_change_mm_sync(struct vdpasim *vdpasim,
>> kthread_flush_work(work);
>> }
>>
>> +static void flush_work_fn(struct kthread_work *work) {}
>> +
>> +static void vdpasim_flush_work(struct vdpasim *vdpasim)
>> +{
>> + struct kthread_work work;
>> +
>> + kthread_init_work(&work, flush_work_fn);
>> + kthread_queue_work(vdpasim->worker, &work);
>> + kthread_flush_work(&work);
>
> Wouldn't it be better to cancel the work with kthread_cancel_work_sync here?
I believe that does not guarantee that currently executing work completes:
static bool __kthread_cancel_work_sync()
if (worker->current_work != work)
goto out_fast;
- Steve
>> +}
>> +
>> static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
>> {
>> return container_of(vdpa, struct vdpasim, vdpa);
>> @@ -512,6 +523,8 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
>> vdpasim->running = false;
>> mutex_unlock(&vdpasim->mutex);
>>
>> + vdpasim_flush_work(vdpasim);
>> +
>> return 0;
>> }
>>
>> --
>> 2.39.3
>>
>
