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

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Date:   Wed, 27 Dec 2017 04:52:37 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Jia Zhang <qianyue.zj@...baba-inc.com>
CC:     "bp@...en8.de" <bp@...en8.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/microcode/intel: Blacklist the specific BDW-EP
 for late loading

When all the patch issues are ironed out consider this 

Acked-by: Tony Luck <tony.luck@...el.com>

I was planning to hunt down the erratum when I got back from vacation in the new year.

Sent from my iPhone

> On Dec 26, 2017, at 04:42, 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");
>        return true;
>    }
> 
> -- 
> 1.8.3.1
>