Re: [Xen-devel] [PATCH] add canonical address checks to HVM

To:	Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] add canonical address checks to HVM
From:	Keir Fraser <keir@xxxxxxxxxxxxx>
Date:	Thu, 30 Nov 2006 17:55:55 +0000
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On 29/11/06 15:05, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> Add proper long mode canonical address checks to PIO emulation and MSR
> writes, the former paralleling the limit checks added for 32-bit guests.
> Also catches two more cases in the MSR handling code where only ECX
> (rather than RCX) should be used.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

I wonder if we would be better consistently *removing* the canonical-address
checks? It's not a security issue after all -- the check is done in hardware
only to prevent code from ever depending on being able to use the high
address bits for software flags. I think it is harmless to deviate from
native behaviour on this issue and makes our emulation code smaller and
simpler.

 -- Keir

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