linux-kernel - Re: [PATCH] x86/cpufeatures: Free up unused feature bits

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Message-ID: <3492e85d-4aaa-4dd7-9e6a-c8fdc2aa2178@intel.com>
Date: Thu, 7 Nov 2024 15:44:57 -0800
From: Sohil Mehta <sohil.mehta@...el.com>
To: Dave Hansen <dave.hansen@...el.com>, <x86@...nel.org>, Borislav Petkov
	<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H .
 Peter Anvin" <hpa@...or.com>, Sean Christopherson <seanjc@...gle.com>, "Tony
 Luck" <tony.luck@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/cpufeatures: Free up unused feature bits

On 11/7/2024 3:36 PM, Dave Hansen wrote:
> On 11/7/24 15:30, Sohil Mehta wrote:
>> Linux defined feature bits X86_FEATURE_P3 and X86_FEATURE_P4 are not
>> used anywhere, neither are they visible to userspace.
>> commit f31d731e4467 ("x86: use X86_FEATURE_NOPL in alternatives") got
>> rid of the last usage. Remove the related mappings and code.
> 
> Hah, not referenced since 2008!  This one seems like a no-brainer.

Thankfully, it wasn't referenced anywhere. For a couple of minutes I was
wondering why all family 6 CPUs are marked as Pentium 3 on 32-bit.

> @@ -628,11 +628,6 @@ static void init_intel(struct cpuinfo_x86 *c)
>  		if (p)
>  			strcpy(c->x86_model_id, p);
>  	}

Here..

> -	if (c->x86 == 6)
> -		set_cpu_cap(c, X86_FEATURE_P3);