target/ppc/spapr: Clear partition table entry when allocating hash table

target/ppc/spapr: Clear partition table entry when allocating hash table

If we allocate a hash page table then we know that the guest won't be
using process tables, so set the partition table entry maintained for
the guest to zero. If this isn't done, then the guest radix bit will
remain set in the entry. This means that when the guest calls
H_REGISTER_PROCESS_TABLE there will be a mismatch between then flags
and the value in spapr->patb_entry, and the call will fail. The guest
will then panic:

Failed to register process table (rc=-4)
kernel BUG at arch/powerpc/platforms/pseries/lpar.c:959

The result being that it isn't possible to boot a hash guest on a P9
system.

Also fix a bug in the flags parsing in h_register_process_table() which
was introduced by the same patch, and simplify the handling to make it
less likely that errors will be introduced in the future. The effect
would have been setting the host radix bit LPCR_HR for a hash guest
using process tables, which currently isn't supported and so couldn't
have been triggered.

Fixes: 00fd075e18 "target/ppc/spapr: Set LPCR:HR when using Radix mode"
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Message-Id: <20190305022102.17610-1-sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>