Re: [Xen-devel] v3.9 - CPU hotplug and microcode earlier loading hits a mutex deadlock (x86_cpu_hotplug_driver_mutex)

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, May 08, 2013 at 04:29:49PM +0200, Borislav Petkov wrote:
> On Wed, May 08, 2013 at 10:03:42AM -0400, Konrad Rzeszutek Wilk wrote:
> 
> [ â snip some funky BIOS code ]
> 
> > [here it shifts and continues on testing each CPU bit]
> > 
> > > Questions over questions...?
> > 
> > I probably went overboard with my answers :-)
> 
> Konrad, you're killing me! :-) You actually went and looked at the
> BIOS disassembly voluntarily. You must be insane, I think you should
> immediately go to the doctor now for a thorough checkup. :-)
> 
> I think I know who I can sling BIOS issues now to.

Great .. :-)
> 
> > > Looks like save_mc_for_early would need another, local mutex to fix that.
> > 
> > Let me try that. Thanks for the suggestion.
> 
> Ok, seriously now: yeah, this was just an idea, it should at least get
> the nesting out of the way.
> 
> About the BIOS deal: you're probably staring at some BIOS out there
> but is this the way that it is actually going to be implemented on
> the physical hotplug BIOS? I mean, I've only heard rumors about IVB
> supporting physical hotplug but do you even have access to such BIOS to
> verify?

Unfortunatly not. I am getting an IvyTown box so hopefully that has this
support. But I thought that Fenghua did since he mentioned in the patch.

Besides that I think this can also appear on VMWare if one is doing 
CPU hotplug and on some HP machines - let me CC the relevant people
extracted from drivers/acpi/processor_driver.c.
(see  https://lkml.org/lkml/2013/5/7/588 for the thread)

Rafael, do you know of any specific Intel hardware that has this implemented?
> 
> All I'm saying is, let's not hurry too much before we actually can
> really trigger this on baremetal.
> 
> Thanks.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --

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