linux-kernel - Re: [PATCH 2/4] x86: Track minimum microcode revision globally v2

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Date:	Thu, 14 Jun 2012 14:20:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
	peterz@...radead.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/4] x86: Track minimum microcode revision globally v2

On Wed, Jun 13, 2012 at 01:20:40PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> For bug workarounds depending on microcode revisions we need to
> know the minimum microcode revision shared by all CPUs.
> 
> This patch adds infrastructure to track this.
> 
> Every time microcode is updated we update a global variable for
> the minimum microcode revision of all the CPUs in the system.
> At boot time we use the lowest available microcode (and warn
> if  they are inconsistent)
> 
> At CPU hotplug or S3 resume time there is a short race window
> where something might run on the CPUs but before the microcode
> update notifier runs. For the current workarounds that need this
> this is acceptable and shouldn't be a problem.
> 
> Only tested on Intel CPUs, but should work for AMD too.
> 
> v2: Use boot_cpu_data.microcode to track minimum revision (H. Peter Anvin)
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---

[ … ]

> +/*
> + * Track the minimum global microcode version.  On early bootup assume
> + * the BIOS set all CPUs to the same revision. If that's not the case
> + * some code may be already running assuming the newer revision, but
> + * there's not much we can do about that (but it's unlikely to be
> + * problem in early bootup)
> + */
> +__cpuinit void boot_update_min_microcode(struct cpuinfo_x86 *c)
> +{	
> +	static int boot_min_microcode;
> +
> +	if (!boot_min_microcode) {
> +		boot_min_microcode = c->microcode;
> +		boot_cpu_data.microcode = c->microcode;
> +	} else if (c->microcode < boot_min_microcode) {
> +		pr_warn("CPU %d has lower microcode revision %x at boot than boot CPU (%x)\n",
> +			smp_processor_id(), 
> +			c->microcode,
> +			boot_min_microcode);
> +		boot_cpu_data.microcode = c->microcode;
> +	}


Apply? [y]es/[n]o/[e]dit/[v]iew patch/[a]ccept all y
Applying: x86: Track minimum microcode revision globally v2
/home/boris/kernel/.git/rebase-apply/patch:52: trailing whitespace.
{
/home/boris/kernel/.git/rebase-apply/patch:60: trailing whitespace.
                        smp_processor_id(), 
warning: 2 lines add whitespace errors.

-- 
Regards/Gruss,
Boris.
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