Re: [Xen-devel] Re: x86_64 SMP support (status update)

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 27 Jun 2005, at 23:15, Nakajima, Jun wrote:

> The nptl01 runs fine on dom0 as long as it
> runs _alone_. It starts failing with presence of domUs. I feel this
> implies some problems with GDT switching. Is there any race you think 
> of
> where modifications to GDT (done by do_update_descriptor) are not be
> visible or deferred?
If you change GDT page mappings (by switching %cr3) but don't change 
GDT linear address or size, I don't know whether we must execute a LGDT 
instruction or not. Currently we don't.
So you might want to try replacing the following test in 
__context_switch():
   if ( p->vcpu_id != n->vcpu_id )
With:
   if ( 1 )
And see if that fixes things...

Even if not, it'd be interesting to find out whether LGDT is 
potentially required in the situation described in my first sentence.
 -- Keir


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