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/[email protected]/
Signed-off-by: John Garry <[email protected]>
---
This patch is intended as something which I can backport to stable.
Series [1] is a proper fix but stuck, but I would not plan to backport
it anyway.
[1] https://lore.kernel.org/linux-scsi/[email protected]/T/#m069f33edd547533301e2af156ebd6badee199dea
diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
index 7d819fc0395e..eb86afb21aab 100644
--- 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;
}
--
2.35.3
On Thu, 23 Jun 2022 20:41:59 +0800, John Garry wrote:
> 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/[email protected]/
>
> [...]
Applied to 5.19/scsi-fixes, thanks!
[1/1] scsi: hisi_sas: Limit max hw sectors for v3 HW
https://git.kernel.org/mkp/scsi/c/fce54ed02757
--
Martin K. Petersen Oracle Linux Engineering