Re: [PATCH v2 1/5] vduse: Remove unnecessary spin lock protection

Yongji Xie
2022-07-13T10:39:22Z

On Wed, Jul 13, 2022 at 1:57 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Jul 06, 2022 at 01:04:59PM +0800, Xie Yongji wrote:
> > Taking iotlb lock to access bounce page in page fault
> > handler is meaningless since vduse_domain_free_bounce_pages()
> > would only be called during file release.
> >
> > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
>
> vduse_domain_free_bounce_pages is not the
> only one taking this lock.

Yes, but only vduse_domain_free_bounce_pages() is to protect
domain->bounce_maps with this lock. In other places, the lock is used
to protect the domain->iotlb.

> This commit log needs more
> analysis documenting all points of access to bounce_maps
> and why vduse_domain_get_bounce_page and file
> release are the only two.
>

OK, I will explain that we actually protect two different variables
(domain->bounce_maps and domain->iotlb) with one lock.

Thanks,
Yongji