[tip:x86/fpu] x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs()

[tip-bot for Andy Lutomirski]

Commit-ID:  fc560a80bac91e512fc37cdfe03a982ef4543c6b
Gitweb: http://git.kernel.org/tip/fc560a80bac91e512fc37cdfe03a982ef4543c6b
Author: Andy Lutomirski 
AuthorDate: Mon, 31 Oct 2016 15:18:43 -0700
Committer:  Ingo Molnar 
CommitDate: Tue, 1 Nov 2016 07:47:53 +0100

x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs()

fpu__init_check_bugs() runs long after the early FPU init, so CR0.TS
will be clear by the time it runs.  The save-and-restore dance would
have been unnecessary anyway, though, as kernel_fpu_begin() would
have been good enough.

Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Rik van Riel 
Cc: Rusty Russell 
Cc: Thomas Gleixner 
Cc: kvm list 
Link: 
http://lkml.kernel.org/r/76d1f1eacb5caead98197d1eb50ac6110ab20c6a.1477951965.git.l...@kernel.org
Signed-off-by: Ingo Molnar 
---
 arch/x86/kernel/fpu/bugs.c | 7 ---
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/kernel/fpu/bugs.c b/arch/x86/kernel/fpu/bugs.c
index aad34aa..d913047 100644
--- a/arch/x86/kernel/fpu/bugs.c
+++ b/arch/x86/kernel/fpu/bugs.c
@@ -23,17 +23,12 @@ static double __initdata y = 3145727.0;
  */
 void __init fpu__init_check_bugs(void)
 {
-   u32 cr0_saved;
s32 fdiv_bug;
 
/* kernel_fpu_begin/end() relies on patched alternative instructions. */
if (!boot_cpu_has(X86_FEATURE_FPU))
return;
 
-   /* We might have CR0::TS set already, clear it: */
-   cr0_saved = read_cr0();
-   write_cr0(cr0_saved & ~X86_CR0_TS);
-
kernel_fpu_begin();
 
/*
@@ -56,8 +51,6 @@ void __init fpu__init_check_bugs(void)
 
kernel_fpu_end();
 
-   write_cr0(cr0_saved);
-
if (fdiv_bug) {
set_cpu_bug(_cpu_data, X86_BUG_FDIV);
pr_warn("Hmm, FPU with FDIV bug\n");

[tip:x86/fpu] x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs()

[tip-bot for Andy Lutomirski]

Commit-ID:  fc560a80bac91e512fc37cdfe03a982ef4543c6b
Gitweb: http://git.kernel.org/tip/fc560a80bac91e512fc37cdfe03a982ef4543c6b
Author: Andy Lutomirski 
AuthorDate: Mon, 31 Oct 2016 15:18:43 -0700
Committer:  Ingo Molnar 
CommitDate: Tue, 1 Nov 2016 07:47:53 +0100

x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs()

fpu__init_check_bugs() runs long after the early FPU init, so CR0.TS
will be clear by the time it runs.  The save-and-restore dance would
have been unnecessary anyway, though, as kernel_fpu_begin() would
have been good enough.

Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Paolo Bonzini 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Rik van Riel 
Cc: Rusty Russell 
Cc: Thomas Gleixner 
Cc: kvm list 
Link: 
http://lkml.kernel.org/r/76d1f1eacb5caead98197d1eb50ac6110ab20c6a.1477951965.git.l...@kernel.org
Signed-off-by: Ingo Molnar 
---
 arch/x86/kernel/fpu/bugs.c | 7 ---
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/kernel/fpu/bugs.c b/arch/x86/kernel/fpu/bugs.c
index aad34aa..d913047 100644
--- a/arch/x86/kernel/fpu/bugs.c
+++ b/arch/x86/kernel/fpu/bugs.c
@@ -23,17 +23,12 @@ static double __initdata y = 3145727.0;
  */
 void __init fpu__init_check_bugs(void)
 {
-   u32 cr0_saved;
s32 fdiv_bug;
 
/* kernel_fpu_begin/end() relies on patched alternative instructions. */
if (!boot_cpu_has(X86_FEATURE_FPU))
return;
 
-   /* We might have CR0::TS set already, clear it: */
-   cr0_saved = read_cr0();
-   write_cr0(cr0_saved & ~X86_CR0_TS);
-
kernel_fpu_begin();
 
/*
@@ -56,8 +51,6 @@ void __init fpu__init_check_bugs(void)
 
kernel_fpu_end();
 
-   write_cr0(cr0_saved);
-
if (fdiv_bug) {
set_cpu_bug(_cpu_data, X86_BUG_FDIV);
pr_warn("Hmm, FPU with FDIV bug\n");