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RE: [Xen-devel] [PATCH] Calculate correct instruction length fordata-fau

To: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Calculate correct instruction length fordata-fault VM exits on VT-x systems
From: Leendert van Doorn <leendert@xxxxxxxxxxxxxx>
Date: Sat, 29 Apr 2006 19:19:44 -0400
Cc: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Khoa Huynh <khoa@xxxxxxxxxx>
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On Sat, 2006-04-29 at 16:48 +0100, Ian Pratt wrote:

> Having a full emulator available certainly enables lots of cool tricks
> (e.g. the taint tracking example in the paper). You wouldn't want to use
> it for all MMIO operations (they're often singletons), but for handling
> batches is would be good. It's certainly a good way of handling the 16b
> issue on Intel.

Why wouldn't you do it on each mmio operation that is not implemented in
the hypervisor? As soon as you have to do the upcall the cost of going
to qemu-dm, or even a miniguest partition, dwarfs the cost of invoking
the emulator.


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