[PATCH 4.19 014/114] powerpc/pseries: Dont fail hash page table insert for bolted mapping

From: Greg Kroah-Hartman
Date: Thu Jan 02 2020 - 17:19:10 EST

From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>

[ Upstream commit 75838a3290cd4ebbd1f567f310ba04b6ef017ce4 ]

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@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20191024093542.29777-2-aneesh.kumar@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
arch/powerpc/mm/hash_utils_64.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index b1007e9a31ba..11b41383e167 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -296,7 +296,14 @@ 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,
+ 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)