linux-kernel - [tip:x86/fpu] x86-32, fpu: Fix DNA exception during check

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Message-ID: <tip-3e7cf5b00dd5b577b4ee9b2a66e40fb670ef210b@git.kernel.org>
Date:	Fri, 1 Jul 2011 00:30:51 GMT
From:	tip-bot for Suresh Siddha <suresh.b.siddha@...el.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	suresh.b.siddha@...el.com, tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/fpu] x86-32, fpu: Fix DNA exception during check_fpu()

Commit-ID:  3e7cf5b00dd5b577b4ee9b2a66e40fb670ef210b
Gitweb:     http://git.kernel.org/tip/3e7cf5b00dd5b577b4ee9b2a66e40fb670ef210b
Author:     Suresh Siddha <suresh.b.siddha@...el.com>
AuthorDate: Thu, 30 Jun 2011 17:19:32 -0700
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 30 Jun 2011 17:29:47 -0700

x86-32, fpu: Fix DNA exception during check_fpu()

Before check_fpu() is called, we have cr0.TS bit set and hence the floating
point code to check the FDIV bug was generating a DNA exception.

Use kernel_fpu_begin()/kernel_fpu_end() around the floating point
code to avoid this unnecessary device not available exception during
boot.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Link: http://lkml.kernel.org/r/1309479572.2665.1372.camel@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 525514c..46674fb 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -62,6 +62,8 @@ static void __init check_fpu(void)
 		return;
 	}
 
+	kernel_fpu_begin();
+
 	/*
 	 * trap_init() enabled FXSR and company _before_ testing for FP
 	 * problems here.
@@ -80,6 +82,8 @@ static void __init check_fpu(void)
 		: "=m" (*&fdiv_bug)
 		: "m" (*&x), "m" (*&y));
 
+	kernel_fpu_end();
+
 	boot_cpu_data.fdiv_bug = fdiv_bug;
 	if (boot_cpu_data.fdiv_bug)
 		printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n");
--
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