Re: [Xen-devel] [PATCH] vmwrite high 32 bits of 64bit VMCS field

To:	"Li, Xin B" <xin.b.li@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] [PATCH] vmwrite high 32 bits of 64bit VMCS fields when in PAE mode
From:	Keir Fraser <keir@xxxxxxxxxxxxx>
Date:	Tue, 10 Jul 2007 23:07:05 +0100
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On 10/7/07 18:57, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:

> Is this necessary? Writes to low halves clear top halves, and these data
> structures will always be below 4GB, right?
> 
> Are you just being super safe? :-)

Oh, furthermore with a 32-bit build of Xen we have to be safe for the case
that VMX_BASIC_MSR[48]==1 (which Vol 3B Appendix G.1 says is true for non
Intel64 CPUs like Yonah). In this case the physical pointers poked into the
VMCS are limited to 32 bits. We may as well limit all such structures to
below 4GB in all cases with a 32-bit build of Xen.

 -- Keir

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Re: [Xen-devel] [PATCH] vmwrite high 32 bits of 64bit VMCS fields when i