powerpc/pseries: Don't fail hash page table insert for bolted mapping

If the hypervisor returned H_PTEG_FULL for H_ENTER hcall, retry a hash page table
insert by removing a random entry from the group.

After some runtime, it is very well possible to find all the 8 hash page table
entry slot in the hpte group used for mapping. Don't fail a bolted entry insert
in that case. With Storage class memory a user can find this error easily since
a namespace enable/disable is equivalent to memory add/remove.

This results in failures as reported below:

$ ndctl create-namespace -r region1 -t pmem -m devdax -a 65536 -s 100M
libndctl: ndctl_dax_enable: dax1.3: failed to enable
  Error: namespace1.2: failed to enable

failed to create namespace: No such device or address

In kernel log we find the details as below:

Unable to create mapping for hot added memory 0xc000042006000000..0xc00004200d000000: -1
dax_pmem: probe of dax1.3 failed with error -14

This indicates that we failed to create a bolted hash table entry for direct-map
address backing the namespace.

We also observe failures such that not all namespaces will be enabled with
ndctl enable-namespace all command.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191024093542.29777-2-aneesh.kumar@linux.ibm.com

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 6c123760164e8f66dcc427e34ba9e4aee44e8031..6e5a769ebcb802ad271a416cee43a23d30e51581 100644 (file)
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -294,7 +294,14 @@ int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
                ret = mmu_hash_ops.hpte_insert(hpteg, vpn, paddr, tprot,
                                               HPTE_V_BOLTED, psize, psize,
                                               ssize);
-
+               if (ret == -1) {
+                       /* Try to remove a non bolted entry */
+                       ret = mmu_hash_ops.hpte_remove(hpteg);
+                       if (ret != -1)
+                               ret = mmu_hash_ops.hpte_insert(hpteg, vpn, paddr, tprot,
+                                                              HPTE_V_BOLTED, psize, psize,
+                                                              ssize);
+               }
                if (ret < 0)
                        break;