Re: Re: Re: [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost device iotlb

On Mon, Apr 12, 2021 at 10:29:17AM +0800, Yongji Xie wrote:

On Mon, Apr 12, 2021 at 4:49 AM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Sun, Apr 11, 2021 at 01:36:18PM +0800, Yongji Xie wrote:

quoted

On Sat, Apr 10, 2021 at 12:16 AM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Wed, Mar 31, 2021 at 04:05:12PM +0800, Xie Yongji wrote:

quoted

Use vhost_dev->mutex to protect vhost device iotlb from
concurrent access.

Fixes: 4c8cf318("vhost: introduce vDPA-based backend")
Cc: stable@vger.kernel.org
Signed-off-by: Xie Yongji <redacted>
Acked-by: Jason Wang <redacted>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

I could not figure out whether there's a bug there now.
If yes when is the concurrent access triggered?

When userspace sends the VHOST_IOTLB_MSG_V2 message concurrently?

vhost_vdpa_chr_write_iter -> vhost_chr_write_iter ->
vhost_vdpa_process_iotlb_msg()

Thanks,
Yongji

And then what happens currently?

Then we might access vhost_vdpa_map() concurrently and cause
corruption of the list and interval tree in struct vhost_iotlb.

Thanks,
Yongji

OK. Sounds like it's actually needed in this release if possible.  Pls
add this info in the commit log and post it as a separate patch. 

-- 
MST

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