x86/traps: Have read_cr0() only once in the #NM handler (ee35b9b9) · Commits · 戴 / test

... 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

arch/x86/kernel/traps.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -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);

Admin message