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

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

On 5/22/2014 3:44 AM, Jan Beulich wrote:
>>>> On 21.05.14 at 23:28, <aravind.gopalakrishnan@amd.com> 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@amd.com>
>> ---
>>   xen/arch/x86/microcode_amd.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
>> index e83f4b6..23637e2 100644
>> --- a/xen/arch/x86/microcode_amd.c
>> +++ b/xen/arch/x86/microcode_amd.c
>> @@ -191,7 +191,7 @@ static int apply_microcode(int cpu)
>>   
>>       spin_lock_irqsave(&microcode_update_lock, flags);
>>   
>> -    wrmsrl(MSR_AMD_PATCHLOADER, (unsigned long)hdr);
>> +    wrmsr_safe(MSR_AMD_PATCHLOADER, (unsigned long)hdr);
> I think you shouldn't ignore the "return" value here.
Not sure I understand..
Do you mean you want to capture return value and bubble it up? maybe 
print a debug message too?
Since we check if patch application succeeded using -
if ( rev != hdr->patch_id )
and return a error val here, would this not be sufficient?

> Also the last quoted log message above has the two revisions
> reversed - mind fixing this at the same time?
>
>
Will fix this.

Thanks,
-Aravind.