linux-kernel - Re: [PATCH v3] x86/microcode/intel: Blacklist the specific BDW-EP for late loading

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Message-ID: <8545e1cc-2722-f7a1-fb30-d57a0da73be2@alibaba-inc.com>
Date:   Tue, 26 Dec 2017 20:36:46 +0800
From:   "Jia Zhang" <qianyue.zj@...baba-inc.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org, tony.luck@...el.com
Subject: Re: [PATCH v3] x86/microcode/intel: Blacklist the specific BDW-EP for
 late loading



在 2017/12/26 下午6:51, Borislav Petkov 写道:
> On Tue, Dec 26, 2017 at 09:44:31AM +0800, Jia Zhang wrote:
>> Instead of blacklisting all Broadwell processorsi for running a late
> 					^^^^^^^^^^^
> 
> Please run all text in this patch through a spellchecker.
> 
>> loading, only BDW-EP (signature 406f1) with the microcode version
> 
> Please write out what that signature actually is - it might be confusing
> to people not dealing with family/model/stepping on a daily basis.
> 
>> less than 0x0b000021 needs to be blacklisted.
>>
>> This is documented in the the public documentation #334165 (See the
>> item BDF90 for details).
>>
>> Signed-off-by: Jia Zhang <qianyue.zj@...baba-inc.com>
>> ---
>>  arch/x86/kernel/cpu/microcode/intel.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
>> index 8ccdca6..d2c1638 100644
>> --- a/arch/x86/kernel/cpu/microcode/intel.c
>> +++ b/arch/x86/kernel/cpu/microcode/intel.c
>> @@ -910,8 +910,15 @@ 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 reault in system hang when running a late
> 			       ^^^^^^
> typo.
> 
>> +	 * 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 < 0x0b000021U) {
> 							    ^
> 
> The appended 'U' is for? I mean, I'd expect the implicit promotion rules
> to kick in here as always. :-)
> 
>> +		pr_err_once("late loading on model 79 (sig 64f1) is disabled.\n");
> 
> See, you can get the sig wrong yourself too. Or were you trying to write
> family/model/stepping in some short form?

Yeah I initially used intel-ucode file naming scheme
family-model-stepping here. It should be changed to use the regular form
of processor signature.

Thanks,
Jia

> 
> Also, this error message needs to explain exactly why late loading is
> disabled - because microcode revision is < 0x0b000021.
>