Re: [virtio-dev] [PATCH v7 2/2] virtio-fs: add DAX window

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 23 Aug 2019 16:39:40 +0100
Stefan Hajnoczi <stefanha@redhat.com> wrote:

> Describe how shared memory region ID 0 is the DAX window and how
> FUSE_SETUPMAPPING maps file ranges into the window.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> The FUSE_SETUPMAPPING message is part of the virtio-fs Linux patches:
> https://gitlab.com/virtio-fs/linux/blob/virtio-fs/include/uapi/linux/fuse.h
> 
> v7:
>  * Clarify that the DAX Window is optional and can be used together with
>    FUSE_READ/FUSE_WRITE requests [Cornelia]
> v6:
>  * Document timing side-channel attacks [Michael]
> ---
>  virtio-fs.tex | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 66 insertions(+) 

(...)

> +\drivernormative{\paragraph}{Device Operation: DAX Window}{Device Types / File System Device / Device Operation / Device Operation: DAX Window}
> +
> +The driver SHOULD be prepared to find shared memory region ID 0 absent and fall back to FUSE\_READ and FUSE\_WRITE requests.
> +
> +The driver MAY use FUSE\_READ and FUSE\_WRITE requests and also access file contents through the DAX Window.

"The driver MAY both use FUSE_READ and FUSE_WRITE requests and access
file contents through the DAX Window." ?

Not sure whether that makes it clearer that it is fine to use a
combination of both methods.

> +
> +The driver MUST NOT access DAX window areas that have not been mapped.
> +

Otherwise, looks good.