On Fri, Oct 10, 2025 at 2:34 PM Michael S. Tsirkin <[email protected]> wrote:
>
...
>
>
> > @@ -2045,11 +2046,11 @@ static int vdpa_dev_add(struct vdpa_mgmt_dev *mdev,
> > const char *name,
> > if (ret)
> > return ret;
> >
> > - mutex_lock(&dev->domain_lock);
> > + write_lock(&dev->domain_lock);
> > if (!dev->domain)
> > dev->domain = vduse_domain_create(VDUSE_IOVA_SIZE - 1,
> > dev->bounce_size);
> > - mutex_unlock(&dev->domain_lock);
> > + write_unlock(&dev->domain_lock);
> > if (!dev->domain) {
> > put_device(&dev->vdev->vdpa.dev);
> > return -ENOMEM;
>
>
> Let's look at this example:
>
> So now you are invoking this under an rw lock:
>
>
>
>
> struct vduse_iova_domain *
> vduse_domain_create(unsigned long iova_limit, size_t bounce_size)
> {
> struct vduse_iova_domain *domain;
> struct file *file;
> struct vduse_bounce_map *map;
> unsigned long pfn, bounce_pfns;
> int ret;
>
> bounce_pfns = PAGE_ALIGN(bounce_size) >> BOUNCE_MAP_SHIFT;
> if (iova_limit <= bounce_size)
> return NULL;
>
> domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> if (!domain)
> return NULL;
>
>
> ...
>
>
>
> Which unless I am mistaken will produce a lockdep splat and deadlock.
>
Can you expand on this? All that code works with and without lockdep.
>
> So it looks like the previous version did not compile
> and this one looks DOA. What's up?
>
In case it is useful, I forgot to enable some vendor vdpa drivers of
HW I don't have, and that was the reason why it didn't compile. But I
didn't send it without testing it of course.
> At this stage please include information about configs you
> tested, and how.
>
> And any locking changes should also be tested with lockdep enabled
> please.
>
This is the text I'm planning to include in the next series, please
let me know if you want me to expand:
Tested by creating a VDUSE device OVS with and without MQ, and live
migrating between two hosts back and forth while maintaining ping
alive in all the stages. All tested with and without lockdep.
