Re: [PATCH v4] x86/microcode/intel: Blacklist the specific BDW-EP for late loading

[Jia Zhang]

å 2017/12/28 äå8:24, Ingo Molnar åé:
> 
> * Jia Zhang <qianyue.zj@xxxxxxxxxxxxxxx> wrote:
> 
>> Instead of blacklisting all types of Broadwell processor when running
>> a late loading, only BDW-EP (signature 0x406f1, aka family 6, model 79,
>> stepping 1) with the microcode version less than 0x0b000021 needs to
>> be blacklisted.
>>
>> The erratum is documented in the the public documentation #334165 (See
>> the item BDF90 for details).
>>
>> Signed-off-by: Jia Zhang <qianyue.zj@xxxxxxxxxxxxxxx>
>> ---
>>  arch/x86/kernel/cpu/microcode/intel.c | 12 ++++++++++--
>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
>> index 8ccdca6..79cad85 100644
>> --- a/arch/x86/kernel/cpu/microcode/intel.c
>> +++ b/arch/x86/kernel/cpu/microcode/intel.c
>> @@ -910,8 +910,16 @@ static bool is_blacklisted(unsigned int cpu)
>>  {
>>  	struct cpuinfo_x86 *c = &cpu_data(cpu);
>>  
>> -	if (c->x86 == 6 && c->x86_model == INTEL_FAM6_BROADWELL_X) {
>> -		pr_err_once("late loading on model 79 is disabled.\n");
>> +	/*
>> +	 * The Broadwell-EP processor with the microcode version less
>> +	 * then 0x0b000021 may result in system hang when running a late
>> +	 * loading. This behavior is documented in item BDF90, #334165
>> +	 * (Intel Xeon Processor E7-8800/4800 v4 Product Family).
>> +	 */
>> +	if (c->x86 == 6 && c->x86_model == INTEL_FAM6_BROADWELL_X &&
>> +	    c->x86_mask == 0x01 && c->microcode < 0x0b000021) {
>> +		pr_err_once("late loading on cpu (sig 0x406f1) is disabled "
>> +			    "due to erratum causing system hang.\n");
> 
> Please never break user-readable messages mid-sentence!
> 
> This should be something like:
> 
> 		pr_err_once("Late loading of the CPU microcode (sig 0x406f1) is disabled due to Intel erratum BDF90 causing system hangs.\n");
> 
> (note the spelling and readability improvements as well)
> 
> Btw., what does 'sig 0x406f1' refer to?

It is so-called processor signature which can be used to identify a
model of x86 processor uniquely. It's the return value of cpuid
instruction with leaf 1(eax == 1).

Jia

> 
> Thanks,
> 
> 
> 	Ingo
>