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[Xen-devel] Re: issues with movnti emulation

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: issues with movnti emulation
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Fri, 21 Nov 2008 11:04:43 +0000
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>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 20.11.08 18:13 >>>
>I think the issue is that I did a bad backport to 3.3. The 'case 0xc3'
>should be under twobyte_special_insn rather than twobyte_insn, right? The
>two separate paths got merged into one in xen-unstable.

Oh, indeed - if you mean it the other way around.

>Of course this data corruption ought only to happen in cases where we'd
>previously have failed an mmio emulation (and hence probably killed the
>guest kernel?).

Yes, we previously saw emulation failure messages. The guest wasn't
killed because of that, however. I have to admit it's been a while since
I last looked at mmio emulation - is it eagerly trying to emulate successive
instructions, and return to native execution when emulation failed? If
not, I could neither explain why only some data got corrupted here, nor
why the guest didn't get killed.

Jan


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