[PATCH 5.10 080/112] scsi: hisi_sas: Limit max hw sectors for v3 HW

Greg Kroah-Hartman
2022-07-19T12:26:03Z

From: John Garry <john.garry@huawei.com>

[ Upstream commit fce54ed027577517df1e74b7d54dc2b1bd536887 ]

If the controller is behind an IOMMU then the IOMMU IOVA caching range can
affect performance, as discussed in [0].

Limit the max HW sectors to not exceed this limit. We need to hardcode the
value until a proper DMA mapping API is available.

[0] https://lore.kernel.org/linux-iommu/20210129092120.1482-1-thunder.leizhen@huawei.com/

Link: https://lore.kernel.org/r/1655988119-223714-1-git-send-email-john.garry@huawei.com
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/hisi_sas/hisi_sas_v3_hw.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
index cd41dc061d87..dfe7e6370d84 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
@@ -2738,6 +2738,7 @@ static int slave_configure_v3_hw(struct scsi_device *sdev)
struct hisi_hba *hisi_hba = shost_priv(shost);
struct device *dev = hisi_hba->dev;
int ret = sas_slave_configure(sdev);
+ unsigned int max_sectors;

if (ret)
return ret;
@@ -2755,6 +2756,12 @@ static int slave_configure_v3_hw(struct scsi_device *sdev)
}
}

+ /* Set according to IOMMU IOVA caching limit */
+ max_sectors = min_t(size_t, queue_max_hw_sectors(sdev->request_queue),
+ (PAGE_SIZE * 32) >> SECTOR_SHIFT);
+
+ blk_queue_max_hw_sectors(sdev->request_queue, max_sectors);
+
return 0;
}

--
2.35.1