From: Andy Lutomirski Date: Wed, 15 Jul 2015 10:29:34 -0700 Subject: [5/9] x86/nmi/64: Remove asm code that saves CR2 Origin: https://git.kernel.org/linus/0e181bb58143cb4a2e8f01c281b0816cd0e4798e Now that do_nmi saves CR2, we don't need to save it in asm. Signed-off-by: Andy Lutomirski Reviewed-by: Steven Rostedt Acked-by: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Ingo Molnar [bwh: Backported to 4.0: adjust filename, context] Signed-off-by: Ben Hutchings --- arch/x86/kernel/entry_64.S | 18 ------------------ 1 file changed, 18 deletions(-) --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1621,29 +1621,11 @@ end_repeat_nmi: call paranoid_entry DEFAULT_FRAME 0 - /* - * Save off the CR2 register. If we take a page fault in the NMI then - * it could corrupt the CR2 value. If the NMI preempts a page fault - * handler before it was able to read the CR2 register, and then the - * NMI itself takes a page fault, the page fault that was preempted - * will read the information from the NMI page fault and not the - * origin fault. Save it off and restore it if it changes. - * Use the r12 callee-saved register. - */ - movq %cr2, %r12 - /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ movq %rsp,%rdi movq $-1,%rsi call do_nmi - /* Did the NMI take a page fault? Restore cr2 if it did */ - movq %cr2, %rcx - cmpq %rcx, %r12 - je 1f - movq %r12, %cr2 -1: - testl %ebx,%ebx /* swapgs needed? */ jnz nmi_restore nmi_swapgs: