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Re: [Xen-devel] [PATCH][UPDATE]Provide fast write emulation path

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][UPDATE]Provide fast write emulation path
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Fri, 15 Feb 2008 11:36:16 +0000
Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>
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At 10:01 +0000 on 15 Feb (1203069706), Keir Fraser wrote:
> I'd like a final ack from Tim on this one before applying.

Ack.  

I read through again and the only thing I can see is a risk that on SMP
guests, a foreign vcpu might change the guest pagetable under our feet,
leading to a risk of using inconsistent mappings for reads and writes.
I think that's OK, though, because
 - we already have similar exposure from vTLB &c, and will do from OOS;
 - a guest with good TLB flush discipline should be entirely safe.

Cheers,

Tim.

> On 15/2/08 06:06, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
> 
> > So, attached updated patch.
> > 
> > Thanks,
> > Kevin
> > 
> >> From: Tian, Kevin
> >> Sent: 2008?$BG/2?$B7n14?$BF| 9:54
> >> 
> >>> From: Tim Deegan [mailto:Tim.Deegan@xxxxxxxxxx]
> >>> Sent: 2008?$BG/2?$B7n12?$BF| 16:26
> >>> 
> >>> At 21:07 +0800 on 30 Jan (1201727271), Xu, Dongxiao wrote:
> >>>> Hi, Tim,
> >>>> 
> >>>> The stop code is:
> >>>> STOP: 0x0000000A (0xF94EAFFC, 0x000000FF, 0x00000001, 0x805434A2)
> >>> 
> >>> I haven't been able to reproduce this crash, but it certainly
> >>> looks like
> >>> the sort of thing a shadow bug would do.  Were you seeing this on a
> >>> particular version of Windows?
> >> 
> >> I think Dongxiao only tried one version of Windows. I'll ask
> >> his help to try
> >> other versions after back from his vacation.
> >> 
> >>> 
> >>> In the meantime, if you're happy with the shadow lock patch,
> >> I think we
> >>> can take it into unstable.
> >> 
> >> That'd be great.
> >> 
> >> Thanks,
> >> Kevn
> >> 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> 
> 

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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