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Re: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ?
- To: Jan Beulich <JBeulich@xxxxxxxxxx>
- From: Keir Fraser <keir@xxxxxxx>
- Date: Thu, 16 Dec 2010 17:03:11 +0000
- Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Christoph Egger <Christoph.Egger@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 16 Dec 2010 09:05:09 -0800
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- Thread-topic: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ?
On 16/12/2010 16:50, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>>>> On 16.12.10 at 17:42, Keir Fraser <keir@xxxxxxx> wrote:
>> The issue is not one of serialisation or code ordering. It is one of
>> memory-access atomicity. Thus it seems to me that volatile is the correct
>
> Indeed, I agree.
>
>> approach therefore. Perhaps *(volatile type *)px = x or, really, even better
>> I should define some {read,write}_atomic{8,16,32,64} accessor functions
>> which use inline asm to absolutely definitely emit a single atomic 'mov'
>> instruction.
>>
>> Make sense?
>
> Yes.
Excellent. I will lay groundwork and fix pte_{read,write}_atomic directly in
-unstable and -4.0-testing. I will then post a proposed fix for EPT to the
list. I don't know that code so well and I may not otherwise catch all
places that require use of the new accessor macros.
-- Keir
> Jan
>
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