linux-kernel - Re: [PATCH] x86/kerrnel/FPU: clear MP bit of cr0

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Message-ID: <373bbdbb-1755-425c-90bf-1bb7d40944cb@intel.com>
Date: Tue, 3 Jun 2025 09:29:48 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Khalid Ali <khaliidcaliy@...il.com>, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/kerrnel/FPU: clear MP bit of cr0

On 5/26/25 01:22, Khalid Ali wrote:
> Clear MP bit when initializing x87 FPU, since what it does
> is making WAIT/FWAIT instructions to react to setting of TS flag.
> Right now TS bit is cleared so MP should be cleared, as it is not
> needed. This should set the bit in defined state.

Hi Khalid,

What is the user visible result of this change?

Could you also give us a little more background about how you came upon
this problem? Was a program misbehaving and you narrowed it down to
this? Did you find it by inspection?