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x86/traps: Have read_cr0() only once in the #NM handler

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... instead of twice in the code. In any case, CR0 ends up being read
once anyway:

1. The CONFIG_MATH_EMULATION case does so and exits.
2. The normal case does it once too.

However, read it on function entry instead to make the code even simpler
to follow.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: x86@kernel.org
Link: https://lkml.kernel.org/r/20190117120728.3811-1-bp@alien8.de
This commit is contained in:
Borislav Petkov 2019-01-17 13:02:05 +01:00
parent 49a57857ae
commit ee35b9b9f6
1 changed files with 2 additions and 3 deletions
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5
arch/x86/kernel/traps.c
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@ -880,12 +880,12 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
dotraplinkage void
do_device_not_available(struct pt_regs *regs, long error_code)
{
unsigned long cr0;
unsigned long cr0 = read_cr0();
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
#ifdef CONFIG_MATH_EMULATION
if (!boot_cpu_has(X86_FEATURE_FPU) && (read_cr0() & X86_CR0_EM)) {
if (!boot_cpu_has(X86_FEATURE_FPU) && (cr0 & X86_CR0_EM)) {
struct math_emu_info info = { };
cond_local_irq_enable(regs);
@ -897,7 +897,6 @@ do_device_not_available(struct pt_regs *regs, long error_code)
#endif
/* This should not happen. */
cr0 = read_cr0();
if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) {
/* Try to fix it up and carry on. */
write_cr0(cr0 & ~X86_CR0_TS);