[PATCH 4.19 089/106] scsi: mpt3sas: fix memory ordering on 64bit writes

From: Greg Kroah-Hartman
Date: Thu Jan 24 2019 - 14:37:57 EST

4.19-stable review patch. If anyone has any objections, please let me know.


[ Upstream commit 23c3828aa2f84edec7020c7397a22931e7a879e1 ]

With commit 09c2f95ad404 ("scsi: mpt3sas: Swap I/O memory read value back
to cpu endianness"), 64bit writes in _base_writeq() were rewritten to use
__raw_writeq() instad of writeq().

This introduced a bug apparent on powerpc64 systems such as the Raptor
Talos II that causes the HBA to drop from the PCIe bus under heavy load and
being reinitialized after a couple of seconds.

It can easily be triggered on affacted systems by using something like

fio --name=random-write --iodepth=4 --rw=randwrite --bs=4k --direct=0 \
--size=128M --numjobs=64 --end_fsync=1
fio --name=random-write --iodepth=4 --rw=randwrite --bs=64k --direct=0 \
--size=128M --numjobs=64 --end_fsync=1

a couple of times. In my case I tested it on both a ZFS raidz2 and a btrfs
raid6 using LSI 9300-8i and 9400-8i controllers.

The fix consists in resembling the write ordering of writeq() by adding a
mandatory write memory barrier before device access and a compiler barrier
afterwards. The additional MMIO barrier is superfluous.

Signed-off-by: Stephan GÃnther <moepi@xxxxxxxxx>
Reported-by: Matt Corallo <linux@xxxxxxxxxxx>
Acked-by: Sreekanth Reddy <Sreekanth.Reddy@xxxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/scsi/mpt3sas/mpt3sas_base.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 59d7844ee022..b59bba3e6516 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -3344,8 +3344,9 @@ _base_mpi_ep_writeq(__u64 b, volatile void __iomem *addr,
static inline void
_base_writeq(__u64 b, volatile void __iomem *addr, spinlock_t *writeq_lock)
+ wmb();
__raw_writeq(b, addr);
- mmiowb();
+ barrier();
static inline void