Patch "powerpc: Add check_if_tm_restore_required() to giveup_all()" has been added to the 4.8-stable tree

Patch "powerpc: Add check_if_tm_restore_required() to giveup_all()" has been added to the 4.8-stable tree

[gregkh]

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

    powerpc: Add check_if_tm_restore_required() to giveup_all()

to the 4.8-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:
     powerpc-add-check_if_tm_restore_required-to-giveup_all.patch
and it can be found in the queue-4.8 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 b0f16b46988fde02a1e32078f66a3059d7e53bfc Mon Sep 17 00:00:00 2001
From: Cyril Bur <cyrilbur@gmail.com>
Date: Fri, 23 Sep 2016 16:18:09 +1000
Subject: powerpc: Add check_if_tm_restore_required() to giveup_all()

From: Cyril Bur <cyrilbur@gmail.com>

commit b0f16b46988fde02a1e32078f66a3059d7e53bfc upstream.

giveup_all() causes FPU/VMX/VSX facilities to be disabled in a threads
MSR. If the thread performing the giveup was transactional, the kernel
must record which facilities were in use before the giveup as the
thread must have these facilities re-enabled on return to userspace.

>>From process.c:
 /*
  * This is called if we are on the way out to userspace and the
  * TIF_RESTORE_TM flag is set.  It checks if we need to reload
  * FP and/or vector state and does so if necessary.
  * If userspace is inside a transaction (whether active or
  * suspended) and FP/VMX/VSX instructions have ever been enabled
  * inside that transaction, then we have to keep them enabled
  * and keep the FP/VMX/VSX state loaded while ever the transaction
  * continues.  The reason is that if we didn't, and subsequently
  * got a FP/VMX/VSX unavailable interrupt inside a transaction,
  * we don't know whether it's the same transaction, and thus we
  * don't know which of the checkpointed state and the transactional
  * state to use.
  */

Calling check_if_tm_restore_required() will set TIF_RESTORE_TM and
save the MSR if needed.

Fixes: c208505 ("powerpc: create giveup_all()")
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/process.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -445,6 +445,7 @@ void giveup_all(struct task_struct *tsk)
 		return;
 
 	msr_check_and_set(msr_all_available);
+	check_if_tm_restore_required(tsk);
 
 #ifdef CONFIG_PPC_FPU
 	if (usermsr & MSR_FP)


Patches currently in stable-queue which might be from cyrilbur@gmail.com are

queue-4.8/powerpc-add-check_if_tm_restore_required-to-giveup_all.patch
queue-4.8/powerpc-always-restore-fpu-vec-vsx-if-hardware-transactional-memory-in-use.patch