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Re: [Xen-devel] [PATCH V2] x86, amd_ucode: Safeguard against #GP

On 5/27/2014 6:47 PM, Andrew Cooper wrote:
On 27/05/2014 19:24, 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.

Also, massage error handling around apply_microcode to keep
in tune with error handling style of other parts of the code.

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
As shown, the log message above has the two revisions reversed. Fix this

Changes in V2:
     - Do not ignore return value from wrmsr_safe
     - Flip revision numbers as shown above

Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
I thought we had identified that the hangs were to do with your use of
'noreboot' on the Xen command line.

Hmm. Yeah.. I figured using wrmsr_safe allows user to just boot into dom0 without
having to run through reboot loops. (lazy alternative I guess)

Nevermind then. Thanks for the comments (Jan and Andrew). Will keep in mind for the future.


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