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

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Date:   Thu, 28 Dec 2017 13:24:29 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Jia Zhang <qianyue.zj@...baba-inc.com>
Cc:     bp@...en8.de, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org, tony.luck@...el.com
Subject: Re: [PATCH v4] x86/microcode/intel: Blacklist the specific BDW-EP
 for late loading


* Jia Zhang <qianyue.zj@...baba-inc.com> 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@...baba-inc.com>
> ---
>  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?

Thanks,


	Ingo