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Re: [Xen-devel] [PATCH] x86/pv: Move async_exception_cleanup() into pv/iret.c


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <JBeulich@xxxxxxxx>
  • Date: Wed, 24 Jul 2019 11:43:45 +0000
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  • Cc: Juergen Gross <JGross@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 24 Jul 2019 11:45:17 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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  • Thread-topic: [Xen-devel] [PATCH] x86/pv: Move async_exception_cleanup() into pv/iret.c

On 24.07.2019 13:04, Andrew Cooper wrote:
> On 24/07/2019 11:22, Jan Beulich wrote:
>> On 23.07.2019 21:58, Andrew Cooper wrote:
>>> All callers are in pv/iret.c.  Move the function and make it static.
>>>
>>> Even before the pinning cleanup, there was nothing which is specific to
>>> operating on curr, so rename the variable back to v.
>> I'm not in full agreement with this: The implication here was (and afaict
>> still is) that uses of / updates to involved vCPU fields are race free.z
>> Feel free to add my ack if you revert back to curr. Otherwise I'd first
>> like to hear your contrary opinion.
> 
> We still call this v in plenty of other cases.

And we still call "curr" "v" in many cases where we shouldn't. I think
it is helpful to know when there are such assumptions, ...

> If it wanted to be strictly limited to current then it should
> ASSERT(curr == current) as it doesn't derive curr itself, but with the
> move and being static, this is very obviously a pointless check, given
> the two callers.

... even when it's only a static helper.

Jan
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