Commit-ID: 71eb3c6d155c54fb74d2f95166162296a8f9af12
Gitweb: http://git.kernel.org/tip/71eb3c6d155c54fb74d2f95166162296a8f9af12
Author: Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Tue, 5 May 2015 10:54:04 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 19 May 2015 15:47:46 +0200
x86/fpu: Make check_fpu() init ordering independent
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@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 400a3d7..449b5f3 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");
--
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