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Re: [PATCH 2/3] gnttab: consolidate pin-to-status syncing
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 15 Jan 2021 13:25:23 +0000
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- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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On 14/01/2021 15:23, Jan Beulich wrote:
> Forever since the fix for XSA-230 the 2nd of the comments ahead of
> fixup_status_for_copy_pin() has been stale - there's nothing specific to
> transitive grants there anymore.
>
> Move the function up, drop the "copy" part from its name again, add a
> "readonly" parameter, and use it also on other paths having decremented
> one (or not having got to increment any) of the pin counts.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -908,6 +908,25 @@ static int _set_status(const grant_entry
> return _set_status_v2(shah, status, rd, act, readonly, mapflag,
> ldomid);
> }
>
> +/*
> + * The status for a grant may indicate that we're taking more access than
> + * the pin requires. Fix up the status to match the pin.
This sentence isn't correct. It will only clear status flags to match a
reduction in the pinned references. IOW it cannot be used in the case
that a grant goes from unpinned to pinned.
How about renaming to clear_status_for_pin() to make this clearer? I
don't think it is worth trying to make the operation more generic.
If so (and with a suitable adjustment to the comment), Reviewed-by:
Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
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