Xen devel - Aug 2007 - [PATCH] Fix races in iret hypercall

Hi!

Attached patch fixes races seen on SMP when multiple HVM guests
execute the iret instruction at the same time.

current vcpu can change in the middle of do_iret().

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>



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On 9/8/07 09:35, "Christoph Egger" <Christoph.Egger@amd.com>
wrote:
> Attached patch fixes races seen on SMP when multiple HVM guests
> execute the iret instruction at the same time.
> 
> current vcpu can change in the middle of do_iret().
This is fine as a cleanup, but it does not fix any bugs!

For two reasons:
 1. Current vcpu *cannot* change in the middle of do_iret(). Xen does not
support involuntary preemption.
 2. HVM guests do not ever execute do_iret(). That function is for pv guests
only.

How did you conclude there was a bug?

 -- Keir


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