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[Xen-ia64-devel] Re: [PATCH] use shared version of iva/dcr

from [Matt Chapman]

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To:	"Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
Subject:	[Xen-ia64-devel] Re: [PATCH] use shared version of iva/dcr
From:	Matt Chapman <matthewc@xxxxxxxxxxxxxxx>
Date:	Tue, 23 Aug 2005 19:52:33 +1000
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On Mon, Aug 22, 2005 at 09:56:57AM -0700, Magenheimer, Dan (HP Labs Fort 
Collins) wrote:
> For dcr, this may not matter, but for iva, there
> are some semantics that need to be checked every
> virtual interrupt delivery.  At a minimum, if virtual
> iva is not private, bits 0-14 should be zeroed
> before every use by Xen, correct?

We could do that, but I don't think it's necessary.  The shared page is
only written directly by paravirtualised guests, and for those guests we
can just define the guest interface such that that field must be zero -
it seems unlikely that any OS would intentionally write that field.
If an OS were to write that field, it just shoots itself in the foot as
exceptions are vectored to the wrong address - no loss of isolation
occurs.

Matt

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