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Re: [Xen-devel] [RFC][PATCH] Emulate instructions in vm86 mode

To: Bastian Blank <bastian@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC][PATCH] Emulate instructions in vm86 mode
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sat, 09 Sep 2006 01:15:28 +0100
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On 8/9/06 23:04, "Bastian Blank" <bastian@xxxxxxxxxxxx> wrote:

>>> That is only on the 'failsafe' stackframe path. It is okay to write zero
>>> values there because we already wrote the real values lower down on the
>>> stack frame (at labels FLT7 to FLT10). In fact you probably shouldn't end up
>>> taking the 'failsafe' path anyway, so the code you remove wouldn't normally
>>> be executed at all unless something in the guest is buggy.
>> Yep, saw that. So I have to recheck that.
> It works correctly with the patch but not without. Can't say why.

That doesn't seem to make sense. It's probably worthwhile working out why
you are taking that 'failsafe' path through create_bounce_frame. If you run
a debug build of Xen, do you get lines of the form 'Pre-exception: xxxxxx ->
xxxxxx' in 'xm dmesg' or on the Xen emergency console?

 -- Keir

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