linux-kernel - Re: [PATCH v2 06/10] x86/mce: Convert multiple if () statements into a switch() statement

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Message-ID: <dcfdba92-7004-413d-8011-12771636d11f@intel.com>
Date: Thu, 24 Oct 2024 14:31:49 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>,
	"Hansen, Dave" <dave.hansen@...el.com>
CC: "bp@...en8.de" <bp@...en8.de>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "hpa@...or.com" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>, "linux-edac@...r.kernel.org"
	<linux-edac@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 06/10] x86/mce: Convert multiple if () statements into
 a switch() statement

On 10/24/2024 9:42 AM, Luck, Tony wrote:
> -       if (c->x86 == 6 && c->x86_model < 0x1A && this_cpu_read(mce_num_banks) > 0)
> +       if (c->x86_vfm < INTEL_NEHALEM_EP && this_cpu_read(mce_num_banks) > 0)
>                 mce_banks[0].init = false;
> 
> Updated code now matches for families before 6 (486, Pentium). 486 would never get
> to this code. But I think from the comments about machine check bank 0 being magic
> that Pentium had some rudimentary support.
> 

As you mentioned it yourself (the last time I was concerned about family
5), the following check should cover this scenario?

> @@ -1924,6 +1924,10 @@ static void apply_quirks_intel(struct cpuinfo_x86 *c)
>         struct mce_bank *mce_banks = this_cpu_ptr(mce_banks_array);
>         struct mca_config *cfg = &mca_cfg;
> 
> +       /* Older CPUs (prior to family 6) don't need quirks. */
> +       if (c->x86_vfm < INTEL_PENTIUM_PRO)
> +               return;
> +


Sohil