linux-kernel - Re: [PATCH V6 1/5] x86/cpufeature: Add facility to check for min microcode revisions

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Date:   Mon, 4 Feb 2019 09:27:49 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, tglx@...utronix.de,
        bp@...en8.de, peterz@...radead.org, mingo@...hat.com
Cc:     ak@...ux.intel.com, eranian@...gle.com
Subject: Re: [PATCH V6 1/5] x86/cpufeature: Add facility to check for min
 microcode revisions

Hi all,

Ping. Any comments on this series?

Thanks,
Kan

On 1/21/2019 4:42 PM, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> For bug workarounds or checks, it is useful to check for specific
> microcode revisions.
> 
> Add a new generic function to match the CPU with stepping.
> Add the other function to check the min microcode revisions for
> the matched CPU.
> A new table format is introduced to facilitate the quirk to
> fill the related information.
> 
> This does not change the existing x86_cpu_id because it's an ABI
> shared with modules, and also has quite different requirements,
> as in no wildcards, but everything has to be matched exactly.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Originally-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> ---
> 
> Changes since V5:
> - Use proper tag
> - Rename x86_cpu_check to x86_cpu_desc, and rename its members
>    the same way as the corresponding members in struct cpuinfo_x86
>    are named.
> - Rename INTEL_CHECK_UCODE to INTEL_CPU_DESC
> - Use EXPORT_SYMBOL_GPL
> 
>   arch/x86/include/asm/cpu_device_id.h | 28 ++++++++++++++++++++++++++++
>   arch/x86/kernel/cpu/match.c          | 31 +++++++++++++++++++++++++++++++
>   2 files changed, 59 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpu_device_id.h b/arch/x86/include/asm/cpu_device_id.h
> index baeba05..f35b303 100644
> --- a/arch/x86/include/asm/cpu_device_id.h
> +++ b/arch/x86/include/asm/cpu_device_id.h
> @@ -11,4 +11,32 @@
>   
>   extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match);
>   
> +/*
> + * Match specific microcode revisions.
> + *
> + * vendor/family/model/stepping must be all set.
> + *
> + * only checks against the boot CPU.  When mixed-stepping configs are
> + * valid for a CPU model, add a quirk for every valid stepping and
> + * do the fine-tuning in the quirk handler.
> + */
> +
> +struct x86_cpu_desc {
> +	__u8	x86;		/* CPU family */
> +	__u8	x86_vendor;	/* CPU vendor */
> +	__u8	x86_model;
> +	__u8	x86_stepping;
> +	__u32	x86_microcode_rev;
> +};
> +
> +#define INTEL_CPU_DESC(mod, step, rev) {			\
> +	.x86 = 6,						\
> +	.x86_vendor = X86_VENDOR_INTEL,				\
> +	.x86_model = mod,					\
> +	.x86_stepping = step,					\
> +	.x86_microcode_rev = rev,				\
> +}
> +
> +extern bool x86_cpu_has_min_microcode_rev(const struct x86_cpu_desc *table);
> +
>   #endif
> diff --git a/arch/x86/kernel/cpu/match.c b/arch/x86/kernel/cpu/match.c
> index 3fed388..4f4bf89 100644
> --- a/arch/x86/kernel/cpu/match.c
> +++ b/arch/x86/kernel/cpu/match.c
> @@ -48,3 +48,34 @@ const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id *match)
>   	return NULL;
>   }
>   EXPORT_SYMBOL(x86_match_cpu);
> +
> +static const struct x86_cpu_desc *
> +x86_match_cpu_with_stepping(const struct x86_cpu_desc *match)
> +{
> +	struct cpuinfo_x86 *c = &boot_cpu_data;
> +	const struct x86_cpu_desc *m;
> +
> +	for (m = match; m->x86 | m->x86_model; m++) {
> +		if (c->x86_vendor != m->x86_vendor)
> +			continue;
> +		if (c->x86 != m->x86)
> +			continue;
> +		if (c->x86_model != m->x86_model)
> +			continue;
> +		if (c->x86_stepping != m->x86_stepping)
> +			continue;
> +		return m;
> +	}
> +	return NULL;
> +}
> +
> +bool x86_cpu_has_min_microcode_rev(const struct x86_cpu_desc *table)
> +{
> +	const struct x86_cpu_desc *res = x86_match_cpu_with_stepping(table);
> +
> +	if (!res || res->x86_microcode_rev > boot_cpu_data.microcode)
> +		return false;
> +
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(x86_cpu_has_min_microcode_rev);
>