Re: [Xen-devel] [PATCH] x86, amd_ucode: Safeguard against #GP

[Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>]

On 5/21/2014 5:08 PM, Andrew Cooper wrote:
> On 21/05/2014 22:28, Aravind Gopalakrishnan wrote:
> > When HW tries to load a corrupted patch, it generates #GP
> > and hangs the system. Use wrmsr_safe instead so that we
> > fail to load microcode gracefully.
> >
> > Example on a Fam15h system-
> > (XEN) microcode: CPU0 collect_cpu_info: patch_id=0x6000626
> > (XEN) microcode: CPU0 size 7870, block size 2586 offset 76 equivID
> > 0x6012 rev 0x6000637
> > (XEN) microcode: CPU0 found a matching microcode update with version
> > 0x6000637 (current=0x6000626)
> > (XEN) traps.c:3073: GPF (0000): ffff82d08016f682 -> ffff82d08022d9f8
> > (XEN) microcode: CPU0 update from revision 0x6000637 to 0x6000626 failed
> >
> > Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>
> I suspect that you will find with a *very* up-to-date master tree, an
> early #GP should result in panic() instead of a hang, following
> 279840d5ea646  (If it doesn't I would be interested to know)
The console log states 'Panic on CPU0'. But system is basically hung 
after that.
(attached snapshot)
> As for the patch itself, is it worth using the failure to purge this
> patch from the cache? Nothing good can come of attempting to load the
> same patch on a different cpu.
I don't think we do..
We only save the patch for apply on resume if 'applied_offset' has a 
value right?
-Aravind.

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