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

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Message-ID: <20250526082414.689-1-khaliidcaliy@gmail.com>
Date: Mon, 26 May 2025 08:22:44 +0000
From: Khalid Ali <khaliidcaliy@...il.com>
To: 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,
	Khalid Ali <khaliidcaliy@...il.com>
Subject: [PATCH] x86/kerrnel/FPU: clear MP bit of cr0

From: Khalid Ali <khaliidcaliy@...il.com>

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.

Signed-off-by: Khalid Ali <khaliidcaliy@...il.com>
---
 arch/x86/kernel/fpu/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 998a08f17e33..2a2b45610b74 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -30,7 +30,7 @@ static void fpu__init_cpu_generic(void)
 		cr4_set_bits(cr4_mask);
 
 	cr0 = read_cr0();
-	cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
+	cr0 &= ~(X86_CR0_TS|X86_CR0_EM|X86_CR0_MP); /* clear TS, EM and MP*/
 	if (!boot_cpu_has(X86_FEATURE_FPU))
 		cr0 |= X86_CR0_EM;
 	write_cr0(cr0);
-- 
2.49.0