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

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: RE: [Xen-devel] Re: x86_64 SMP support (status update)
From: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Date: Mon, 27 Jun 2005 15:35:42 -0700
Cc: Chris Wright <chrisw@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Thread-topic: [Xen-devel] Re: x86_64 SMP support (status update)
Keir Fraser wrote:
> 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...

Actually I already tried that, but it did not help...

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

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