Re: [Xen-devel] svm vmexit action sequence

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

See the unstable staging tree for some changes already in this area. As you
can see there is still quite some scope for improvement - I bet we can just
get rid of this push/popf pair for example. And the horrendous
VMLOAD/VMSAVE/VMLOAD/VMSAVE sequence can probably be shoved off at least to
only context switches.

 -- Keir

On 11/5/07 08:28, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> One more question: both variants have HVM_SAVE_ALL_NOSEGREGS do a
> forced reset of eflags/rflags - what is this needed for? #VMEXIT supposedly
> restores them. Jan
> 
>>>> "Petersson, Mats" <Mats.Petersson@xxxxxxx> 10.05.07 18:12 >>>
> 
> 
>> -----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.
> 
> --
> Mats
>> 
>> Thanks, Jan
>> 
>> 
>> 
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>> 
>> 
> 
> 
> 
> 
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