Patch "x86/nmi/64: Remove asm code that saves CR2" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

x86/nmi/64: Remove asm code that saves CR2

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     x86-nmi-64-remove-asm-code-that-saves-cr2.patch

and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andy Lutomirski <[email protected]>
Date: Wed, 15 Jul 2015 10:29:34 -0700
Subject: x86/nmi/64: Remove asm code that saves CR2

From: Andy Lutomirski <[email protected]>

commit 0e181bb58143cb4a2e8f01c281b0816cd0e4798e upstream.

Now that do_nmi saves CR2, we don't need to save it in asm.

---
 arch/x86/kernel/entry_64.S |   18 ------------------
 1 file changed, 18 deletions(-)

@@ -1885,28 +1885,10 @@ end_repeat_nmi:
 	call save_paranoid
 	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

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/x86-nmi-64-use-df-to-avoid-userspace-rsp-confusing-nested-nmi-detection.patch queue-3.14/x86-nmi-enable-nested-do_nmi-handling-for-64-bit-kernels.patch queue-3.14/x86-nmi-64-remove-asm-code-that-saves-cr2.patch queue-3.14/x86-nmi-64-switch-stacks-on-userspace-nmi-entry.patch queue-3.14/x86-nmi-64-improve-nested-nmi-comments.patch queue-3.14/x86-nmi-64-reorder-nested-nmi-checks.patch