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Subject[tip:x86/fpu] x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs()
Commit-ID:  fc560a80bac91e512fc37cdfe03a982ef4543c6b
Gitweb: http://git.kernel.org/tip/fc560a80bac91e512fc37cdfe03a982ef4543c6b
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Mon, 31 Oct 2016 15:18:43 -0700
Committer: Ingo Molnar <mingo@kernel.org>
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 <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm list <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/76d1f1eacb5caead98197d1eb50ac6110ab20c6a.1477951965.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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(&boot_cpu_data, X86_BUG_FDIV);
pr_warn("Hmm, FPU with FDIV bug\n");
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