Re: [Xen-devel] [PATCH] Fix shared entry status for grant copy operation on paged out gfn

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.08.12 at 16:32, Andres Lagar-Cavilla <andreslc@xxxxxxxxxxxxxx> wrote:

> On Aug 22, 2012, at 10:21 AM, Jan Beulich wrote:
> 
>>>>> On 21.08.12 at 22:13, Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> 
>>>>> wrote:
>>> xen/common/grant_table.c |  33 ++++++++++++++++++++++-----------
>>> 1 files changed, 22 insertions(+), 11 deletions(-)
>>> 
>>> 
>>> The unwind path was not clearing the shared entry status bits. This was
>>> BSOD-ing guests on network activity under certain configurations.
>>> 
>>> Also:
>>> * sed the fixup method name to signal it's related to grant copy.
>>> * use atomic clear flag ops during fixup.
>> 
>> Is that last thing really needed? I remember having looked at
>> these non-atomic operations too a little while back, and came to
>> the conclusion that probably the authors intentionally coded it
>> that way.
> 
> Due to some obscure property of transitive grants? All other flag 
> clearing/setting in shared grant entries by the hypervisor is done atomically 
> (GTF_transfer_completed being an exception).
> 
> From my p.o.v. there is no downside. But I am not 100% certain and I can 
> back it off.

Only if they read the thread and respond with an explanation.
After all, the change is certainly not wrong, just slightly slowing
things down.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel