powerpc: Add check_if_tm_restore_required() to giveup_all()
authorCyril Bur <cyrilbur@gmail.com>
Fri, 23 Sep 2016 06:18:09 +0000 (16:18 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Tue, 4 Oct 2016 05:43:06 +0000 (16:43 +1100)
commitb0f16b46988fde02a1e32078f66a3059d7e53bfc
treec34bb3f61c853e1b91d46f3c003127e695bba4c5
parentdc16b553c949e81f37555777dc7bab66d78285a7
powerpc: Add check_if_tm_restore_required() to giveup_all()

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>
arch/powerpc/kernel/process.c