Commit-ID: 9a89b02918c03d91e685d06e49a652da5f35befc
Gitweb: http://git.kernel.org/tip/9a89b02918c03d91e685d06e49a652da5f35befc
Author: Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Thu, 23 Apr 2015 11:26:08 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 19 May 2015 15:47:22 +0200
x86/fpu: Print out whether we are doing lazy/eager FPU context switches
Ever since the kernel started defaulting to eager FPU switches on modern Intel
CPUs it's not been obvious whether a given system is using the lazy or the eager
FPU context switching logic.
So generate a boot message about which mode the FPU code is in:
x86/fpu: Using 'lazy' FPU context switches.
or:
x86/fpu: Using 'eager' FPU context switches.
Reviewed-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
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/xsave.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/fpu/xsave.c b/arch/x86/kernel/fpu/xsave.c
index a52205b..61696c5 100644
--- a/arch/x86/kernel/fpu/xsave.c
+++ b/arch/x86/kernel/fpu/xsave.c
@@ -691,6 +691,8 @@ void __init_refok eager_fpu_init(void)
if (eagerfpu == ENABLE)
setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
+ printk_once(KERN_INFO "x86/fpu: Using '%s' FPU context switches.\n", eagerfpu == ENABLE ? "eager" : "lazy");
+
if (!cpu_has_eager_fpu) {
stts();
return;
--
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