[patch] x32, fpu: fix DNA exception during check_fpu()

[patch] x32, fpu: fix DNA exception during check_fpu()

[Suresh Siddha]

From: Suresh Siddha <suresh.b.siddha@intel.com>

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@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");

[tip:x86/fpu] x86-32, fpu: Fix DNA exception during check_fpu()

[tip-bot for Suresh Siddha]

Commit-ID:  3e7cf5b00dd5b577b4ee9b2a66e40fb670ef210b
Gitweb:     http://git.kernel.org/tip/3e7cf5b00dd5b577b4ee9b2a66e40fb670ef210b
Author:     Suresh Siddha <suresh.b.siddha@intel.com>
AuthorDate: Thu, 30 Jun 2011 17:19:32 -0700
Committer:  H. Peter Anvin <hpa@linux.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@intel.com>
Link: http://lkml.kernel.org/r/1309479572.2665.1372.camel@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.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");

Re: [patch] x32, fpu: fix DNA exception during check_fpu()

[Linus Torvalds]

On Thu, Jun 30, 2011 at 5:19 PM, Suresh Siddha
<suresh.b.siddha@intel.com> wrote:
>
> 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.

Looks sane to me. I didn't think we were supposed to set the TS bit
this early, but if we do, Ack.

                 Linus