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Re: [PATCH 2/3] gnttab: consolidate pin-to-status syncing

  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Fri, 15 Jan 2021 13:37:02 +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>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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On 15/01/2021 13:33, Jan Beulich wrote:
> On 15.01.2021 14:25, Andrew Cooper wrote:
>> On 14/01/2021 15:23, Jan Beulich wrote:
>>> --- 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.
> Of course not, hence "... more access than ...". But yes, I can
> replace "Fix up" by "Reduce" if you think the wording isn't
> unambiguous enough.
>> 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.
> Hmm, this name would suggest to me that the function clears
> whatever the present pin count requires (e.g. acting on the
> pre-update value when the post-update one is [going to be]
> zero). Maybe reduce_status_for_pin(), matching the suggested
> comment wording change?

Sounds good.  My R-by stands with this change.




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