lkml.org 
[lkml]   [2015]   [May]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 122/208] x86/fpu: Make check_fpu() init ordering independent
Date
check_fpu() currently relies on being called early in the init sequence,
when CR0::TS has not been set up yet.

Save/restore CR0::TS across this function, to make it invariant to
init ordering. This way we'll be able to move the generic FPU setup
routines earlier in the init sequence.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/fpu/bugs.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/fpu/bugs.c b/arch/x86/kernel/fpu/bugs.c
index 400a3d713fb2..449b5f3f4925 100644
--- a/arch/x86/kernel/fpu/bugs.c
+++ b/arch/x86/kernel/fpu/bugs.c
@@ -23,8 +23,13 @@ static double __initdata y = 3145727.0;
*/
static void __init check_fpu(void)
{
+ u32 cr0_saved;
s32 fdiv_bug;

+ /* We might have CR0::TS set already, clear it: */
+ cr0_saved = read_cr0();
+ write_cr0(cr0_saved & ~X86_CR0_TS);
+
kernel_fpu_begin();

/*
@@ -47,6 +52,8 @@ static void __init check_fpu(void)

kernel_fpu_end();

+ write_cr0(cr0_saved);
+
if (fdiv_bug) {
set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);
pr_warn("Hmm, FPU with FDIV bug\n");
--
2.1.0


\
 
 \ /
  Last update: 2015-05-05 21:01    [W:0.571 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site