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RE: [Xen-devel] svm vmexit action sequence

  • To: "Jan Beulich" <jbeulich@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Thu, 10 May 2007 18:12:53 +0200
  • Delivery-date: Thu, 10 May 2007 09:11:38 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AceTHIlC+J9wtDWtQ9+wB/B1AY+O9gAANjRQ
  • Thread-topic: [Xen-devel] svm vmexit action sequence


> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Jan Beulich
> Sent: 10 May 2007 17:02
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] svm vmexit action sequence
> Is there any particular reason why on 32-bits the order is VMLOAD then
> HVM_SAVE_ALL_NOSEGREGS, while on 64-bits its is the other way around?
> Trying to put in the saving of EAX, I could save a 
> GET_CURRENT() on 32-bits
> if I could order things the same way as on 64-bits.

I don't see any reason why these shouldn't be the same (or at least as
similar as possible).
> Also, both versions seem to have a redundant GET_CURRENT() right after
> the clgi/sti sequence - again, is there a particular reason for this?

No reason as far as I can tell. Assuming rbx (in 64-bit case) isn't
clobbered by called functions, that is. I can't remember for 64-bit if
rbx is "safe" or not. [It certainly is safe in 32-bit]. 

Thanks for spotting these things.

> Thanks, Jan
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