Patch "MIPS: lose_fpu(): Disable FPU when MSA enabled" has been added to the 3.19-stable tree

Patch "MIPS: lose_fpu(): Disable FPU when MSA enabled" has been added to the 3.19-stable tree

[gregkh]

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

    MIPS: lose_fpu(): Disable FPU when MSA enabled

to the 3.19-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:
     mips-lose_fpu-disable-fpu-when-msa-enabled.patch
and it can be found in the queue-3.19 subdirectory.

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


>From acaf6a97d623af123314c2f8ce4cf7254f6b2fc1 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Wed, 25 Feb 2015 13:08:05 +0000
Subject: MIPS: lose_fpu(): Disable FPU when MSA enabled

From: James Hogan <james.hogan@imgtec.com>

commit acaf6a97d623af123314c2f8ce4cf7254f6b2fc1 upstream.

The lose_fpu() function only disables the FPU in CP0_Status.CU1 if the
FPU is in use and MSA isn't enabled.

This isn't necessarily a problem because KSTK_STATUS(current), the
version of CP0_Status stored on the kernel stack on entry from user
mode, does always get updated and gets restored when returning to user
mode, but I don't think it was intended, and it is inconsistent with the
case of only the FPU being in use. Sometimes leaving the FPU enabled may
also mask kernel bugs where FPU operations are executed when the FPU
might not be enabled.

So lets disable the FPU in the MSA case too.

Fixes: 33c771ba5c5d ("MIPS: save/disable MSA in lose_fpu")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9323/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/include/asm/fpu.h |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/mips/include/asm/fpu.h
+++ b/arch/mips/include/asm/fpu.h
@@ -169,6 +169,7 @@ static inline void lose_fpu(int save)
 		}
 		disable_msa();
 		clear_thread_flag(TIF_USEDMSA);
+		__disable_fpu();
 	} else if (is_fpu_owner()) {
 		if (save)
 			_save_fp(current);


Patches currently in stable-queue which might be from james.hogan@imgtec.com are

queue-3.19/mips-lose_fpu-disable-fpu-when-msa-enabled.patch
queue-3.19/mips-kvm-handle-msa-disabled-exceptions-from-guest.patch