Re: [PATCH] xen/privcmd: Only claim ioreqs matching an ioeventfd

[Juergen Gross]

On 21.08.26 10:41, Koichiro Den wrote:
> The ioeventfd handler shares its event channel with the userspace device
> model. It must only claim requests that match a registered ioeventfd.
> Other requests are left for userspace.
>
> ioeventfd_interrupt() currently marks every MMIO write INPROCESS before
> looking for a match. For an unmatched request it drops the lock and
> restores READY. Userspace may see INPROCESS and skip it. Restoring READY
> does not send another notification. If userspace handles the request at
> the same time, the READY store may overwrite its state.
>
> Find a matching ioeventfd before changing the request state.
>
> The lock now protects only the ioeventfd list. Use explicit virt_*mb()
> barriers for the ioreq shared with Xen.
>
> Fixes: f0d7db7b3324 ("xen: privcmd: Add support for ioeventfd")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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