linux-kernel - [PATCH 4.8 111/125] powerpc: Add check_if_tm_restore_required() to giveup

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Date:   Sat, 29 Oct 2016 09:50:29 -0400
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Cyril Bur <cyrilbur@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.8 111/125] powerpc: Add check_if_tm_restore_required() to giveup_all()

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cyril Bur <cyrilbur@...il.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@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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)