Re: [Xen-devel] [PATCH] Fixing PAE SMP dom0 hang at boot time

[Ryan Harper <ryanh@xxxxxxxxxx>]

* Nakajima, Jun <jun.nakajima@xxxxxxxxx> [2005-11-16 11:42]:
> Ryan Harper wrote:
> > * Nakajima, Jun <jun.nakajima@xxxxxxxxx> [2005-11-15 19:56]:
> >> This patch fixes a hang with PAE SMP dom0 on big SMP machines. As
> >> far as I tested, 8-way PAE SMP dom0 boots fine on >=8-way machines.
> >> The fix is not PAE specific, and I made the equivent changes to
> >> x86_64 xenlinux. Tested on both PAE and x86_64 dom0 xenlinux on
> >> >=8-way SMP machines with 
> >>> 6GB.
> > 
> > Jun,  could you explain the patch a bit more?
> > 
> > Why wouldn't we want to initialize the per-cpu gdt area for cpus other
> > than CPU0 ?
> > 
> > -       cpu_gdt_init(&cpu_gdt_descr[cpu]);
> > +       if (!cpu)
> > +           cpu_gdt_init(&cpu_gdt_descr[cpu]);
> 
> CPU0 creates the (virutal) gdt for other CPUs in advance at
> VCPUOP_initalise, and the propoer selector values are set up at the
> same. So it's redundant. It also avoids spurious page faults caused by
> make_page_readonly() against the gdt page. 

OK.  Thanks for the explaination.  With this patch, we are still seeing
the revised set_gdt() issue (comment 18 on bug 366) on our 32-way.
We've don't seen the hang except when we have 8 cpus instead of the full
32.


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh@xxxxxxxxxx

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