H_ENTER hcall handling in qemu had assumptions that a cache inhibited
hpte entry won't have memory conference set. Also older kernel
mentioned that some version of pHyp required this (the code removed
by the below commit says:
/* Make pHyp happy */
if ((rflags & _PAGE_NO_CACHE) && !(rflags & _PAGE_WRITETHRU))
hpte_r &= ~HPTE_R_M;
But with older kernel we had some inconsistent memory conherence
mapping. We always enabled memory conherence in the page fault path and
removed memory conherence is _PAGE_NO_CACHE was set when we mapped the
page via htab_bolt_mapping. The commit mentioned below tried to
consolidate that by always enabling memory conherence. But as mentioned
above that breaks Qemu H_ENTER handling.
This patch update this such that we enable memory conherence only if
cache inhibited is not set and bring fault handling, lpar and bolt
mapping in sync.
Fixes: commit 30bda41aba4e("powerpc/mm: Drop WIMG in favour of new constant")
Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
e568006b9d