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Re: [Xen-devel] [PATCH] retry instruction on svm emulation failure

  • To: Paolo Bonzini <pbonzini@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Wed, 18 May 2011 11:08:30 +0100
  • Cc:
  • Delivery-date: Wed, 18 May 2011 03:09:14 -0700
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  • Thread-topic: [Xen-devel] [PATCH] retry instruction on svm emulation failure

On 18/05/2011 10:05, "Paolo Bonzini" <pbonzini@xxxxxxxxxx> wrote:

> retry instruction on svm emulation failure
> Upon emulation failure, Xen injects a #GP into the guest on AMD machines.
> However, this kind of #GP does not happen in hardware.  It is possible
> (and was observed in practice) that the failure is transient.  It will
> go away naturally if the instruction is retried, because the guest will
> be executing other code and will not exit.

It begs the question why we were emulating the instruction in the first
place. I'd like to see further explanation, with a concrete example, before
applying this patch. Or get an Ack from an AMD maintainer.

 -- Keir

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