powerpc/watchpoint: Fix quadword instruction handling on p10 predecessors

powerpc/watchpoint: Fix quadword instruction handling on p10 predecessors

[ Upstream commit 4759c11ed20454b7b36db4ec15f7d5aa1519af4a ]

On p10 predecessors, watchpoint with quadword access is compared at
quadword length. If the watch range is doubleword or less than that
in a first half of quadword aligned 16 bytes, and if there is any
unaligned quadword access which will access only the 2nd half, the
handler should consider it as extraneous and emulate/single-step it
before continuing.

Fixes: 74c6881019b7 ("powerpc/watchpoint: Prepare handler to handle more than one watchpoint")
Reported-by: Pedro Miraglia Franco de Carvalho <pedromfc@linux.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200902042945.129369-2-ravi.bangoria@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>