From: Dave Hansen <dave.hansen@intel.com>
To: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>, Len Brown <len.brown@intel.com>,
x86@kernel.org, Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [tip: x86/cpu] x86/cpu/intel: Replace PAT erratum model/family magic numbers with symbolic IFM references
Date: Tue, 3 Sep 2024 11:46:52 -0700 [thread overview]
Message-ID: <c9f18ae0-8239-495a-abc2-d6538fbe5f5e@intel.com> (raw)
In-Reply-To: <172535592591.2215.9909836777026903684.tip-bot2@tip-bot2>
On 9/3/24 02:32, tip-bot2 for Dave Hansen wrote:
> - if (c->x86 == 6 && c->x86_model < 15)
> + if (c->x86_vfm >= INTEL_PENTIUM_PRO &&
> + c->x86_vfm <= INTEL_CORE_YONAH)
> clear_cpu_cap(c, X86_FEATURE_PAT);
Andy Cooper did point out that there is a theoretical behavioral change
here with c->x86_model==0. There is a reference to the existence of
such a beast on at least on random web page[1] on the Internet as "P6
A-step".
But the SDM neither confirms nor denies that such a model ever existed.
If the SDM can't be bothered to acknowledge its existence, Linux
probably shouldn't either.
Either way, we're talking about a 32-bit CPU that's almost 30 years old
and was probably pre-production anyway.
I'm fine with the patch as-is.
1. https://www.sandpile.org/x86/cpuid.htm
next prev parent reply other threads:[~2024-09-03 18:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-29 22:00 [PATCH] x86/cpu/intel: Replace PAT erratum model/family magic numbers Dave Hansen
2024-09-03 9:32 ` [tip: x86/cpu] x86/cpu/intel: Replace PAT erratum model/family magic numbers with symbolic IFM references tip-bot2 for Dave Hansen
2024-09-03 18:46 ` Dave Hansen [this message]
2024-09-04 18:17 ` Andrew Cooper
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