scsi: mpt3sas: fix memory ordering on 64bit writes

moepinet · martinkpetersen · commit 23c3828aa2f8 · 2018-12-19T21:31:41.000-05:00
With commit 09c2f95 ("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 Günther <moepi@moepi.net> Reported-by: Matt Corallo <linux@bluematt.me> Acked-by: Sreekanth Reddy <Sreekanth.Reddy@broadcom.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -3345,8 +3345,9 @@ _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();
 }
 #else
 static inline void

Original file line number	Diff line number	Diff line change
`@@ -3345,8 +3345,9 @@ _base_mpi_ep_writeq(__u64 b, volatile void __iomem *addr,`
`3345`	`3345`	`static inline void`
`3346`	`3346`	`_base_writeq(__u64 b, volatile void __iomem addr, spinlock_t writeq_lock)`
`3347`	`3347`	`{`
	`3348`	`+ wmb();`
`3348`	`3349`	`__raw_writeq(b, addr);`
`3349`		`- mmiowb();`
	`3350`	`+ barrier();`
`3350`	`3351`	`}`
`3351`	`3352`	`#else`
`3352`	`3353`	`static inline void`