Patch "x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround" has been added to the 3.4-stable tree

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

    x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround

to the 3.4-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-fpu-amd-clear-exceptions-in-amd-fxsave-workaround.patch
and it can be found in the queue-3.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 26bef1318adc1b3a530ecc807ef99346db2aa8b0 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Sat, 11 Jan 2014 19:15:52 -0800
Subject: x86, fpu, amd: Clear exceptions in AMD FXSAVE workaround

From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

commit 26bef1318adc1b3a530ecc807ef99346db2aa8b0 upstream.

Before we do an EMMS in the AMD FXSAVE information leak workaround we
need to clear any pending exceptions, otherwise we trap with a
floating-point exception inside this code.

Reported-by: halfdog <me@xxxxxxxxxxx>
Tested-by: Borislav Petkov <bp@xxxxxxx>
Link: http://lkml.kernel.org/r/CA%2B55aFxQnY_PCG_n4=0w-VG=YLXL-yr7oMxyy0WU2gCBAf3ydg@xxxxxxxxxxxxxx
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/include/asm/fpu-internal.h |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -266,12 +266,13 @@ static inline int restore_fpu_checking(s
 	/* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
 	   is pending.  Clear the x87 state here by setting it to fixed
 	   values. "m" is a random variable that should be in L1 */
-	alternative_input(
-		ASM_NOP8 ASM_NOP2,
-		"emms\n\t"		/* clear stack tags */
-		"fildl %P[addr]",	/* set F?P to defined value */
-		X86_FEATURE_FXSAVE_LEAK,
-		[addr] "m" (tsk->thread.fpu.has_fpu));
+	if (unlikely(static_cpu_has(X86_FEATURE_FXSAVE_LEAK))) {
+		asm volatile(
+			"fnclex\n\t"
+			"emms\n\t"
+			"fildl %P[addr]"	/* set F?P to defined value */
+			: : [addr] "m" (tsk->thread.fpu.has_fpu));
+	}
 
 	return fpu_restore_checking(&tsk->thread.fpu);
 }


Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are

queue-3.4/x86-fpu-amd-clear-exceptions-in-amd-fxsave-workaround.patch
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