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

... 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

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a7358ce19741de1c875a75e8f52f8e..2684a9d11e6612541b10731c51bdb9d493ed0d6e 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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);