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

[Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>]

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@amd.com>
>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> 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.

-Aravind.