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

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Message-ID: <c3bb0055-49c5-4e0f-a9bb-8f56e862e11c@intel.com>
Date: Tue, 22 Oct 2024 23:47:43 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>, "Luck, Tony" <tony.luck@...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 10/18/2024 10:46 PM, Zhuo, Qiuxu wrote:
> Convert some hard-coded numbers to VFM macros on top of Tony's patch as shown below. 
> Please review it for any errors or omissions.
> 
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index f51fb393d369..3b83efa1ca65 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -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 don't need quirks. */
> +       if (c->x86 < 6)
> +               return;
> +

As Dave mentioned, change this to make the use of vfm consistent in the
entire function and probably update the comment as well to make it explicit:

	/* Older CPUs (prior to family 6) don't need quirks */
	if (c->x86_vfm < INTEL_PENTIUM_PRO)
		return;


>         /*
>          * SDM documents that on family 6 bank 0 should not be written
>          * because it aliases to another special BIOS controlled
> @@ -1932,23 +1936,21 @@ static void apply_quirks_intel(struct cpuinfo_x86 *c)
>          * Don't ignore bank 0 completely because there could be a
>          * valid event later, merely don't write CTL0.
>          */
> -
> -       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;
> 
>         /*
>          * All newer Intel systems support MCE broadcasting. Enable
>          * synchronization with a one second timeout.
>          */
> -       if ((c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xe)) &&
> -           cfg->monarch_timeout < 0)
> +       if (c->x86_vfm >= INTEL_CORE_YONAH && cfg->monarch_timeout < 0)
>                 cfg->monarch_timeout = USEC_PER_SEC;
> 

Instead of keeping this open-ended we could tweak this a bit as follows:

if (!(c->x86_vfm < INTEL_CORE_YONAH)) && cfg->monarch_timeout < 0)
	cfg->monarch_timeout = USEC_PER_SEC;

Essentially the same: if (new_cpu) vs if (!old_cpu)
Don't have a strong preference. Will leave it to you and Tony.

>         /*
>          * There are also broken BIOSes on some Pentium M and
>          * earlier systems:
>          */
> -       if (c->x86 == 6 && c->x86_model <= 13 && cfg->bootlog < 0)
> +       if (c->x86_vfm < INTEL_CORE_YONAH && cfg->bootlog < 0)
>                 cfg->bootlog = 0;
> 
>         if (c->x86_vfm == INTEL_SANDYBRIDGE_X)
> 

All the other checks look fine to me.