scsi: hisi_sas: Limit max hw sectors for v3 HW

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>

diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
index 7d819fc0395e4a08fdc0e05a4db5ce00935f28b8..eb86afb21aabb692756693683c5c2c2bda21c183 100644 (file)
--- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
@@ -2782,6 +2782,7 @@ 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;
@@ -2799,6 +2800,12 @@ 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;
 }