CC : linux-scsi@xxxxxxxxxxxxxxx, jejb@xxxxxxxxxxxxx, martin.petersen@xxxxxxxxxx
On Fri, Jun 10, 2022 at 09:33:44AM -0700, Saurabh Sengar wrote:
> This patch corrects 3 parameters:
> 1. Correct the sysfs entry for maximum hardware transfer limit of single
> transfer (max_hw_sectors_kb) by setting max_sectors, this was set to
> default value 512kb before.
> 2. Correct SGL memory offset alignment as per Hyper-V page size.
> 3. Correct sg_tablesize which accounts for max SGL segments entries in a
> single SGL.
>
> Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/scsi/storvsc_drv.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index ca3530982e52..3e032660ae36 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1844,7 +1844,7 @@ static struct scsi_host_template scsi_driver = {
> .cmd_per_lun = 2048,
> .this_id = -1,
> /* Ensure there are no gaps in presented sgls */
> - .virt_boundary_mask = PAGE_SIZE-1,
> + .virt_boundary_mask = HV_HYP_PAGE_SIZE - 1,
> .no_write_same = 1,
> .track_queue_depth = 1,
> .change_queue_depth = storvsc_change_queue_depth,
> @@ -1969,11 +1969,31 @@ static int storvsc_probe(struct hv_device *device,
> /* max cmd length */
> host->max_cmd_len = STORVSC_MAX_CMD_LEN;
>
> + /* max_hw_sectors_kb */
> + host->max_sectors = (stor_device->max_transfer_bytes) >> 9;
> /*
> - * set the table size based on the info we got
> - * from the host.
> + * There are 2 requirements for Hyper-V storvsc sgl segments,
> + * based on which the below calculation for max segments is
> + * done:
> + *
> + * 1. Except for the first and last sgl segment, all sgl segments
> + * should be align to HV_HYP_PAGE_SIZE, that also means the
> + * maximum number of segments in a sgl can be calculated by
> + * dividing the total max transfer length by HV_HYP_PAGE_SIZE.
> + *
> + * 2. Except for the first and last, each entry in the SGL must
> + * have an offset that is a multiple of HV_HYP_PAGE_SIZE,
> + * whereas the complete length of transfer may not be aligned
> + * to HV_HYP_PAGE_SIZE always. This can result in 2 cases:
> + * Example for unaligned case: Let's say the total transfer
> + * length is 6 KB, the max segments will be 3 (1,4,1).
> + * Example for aligned case: Let's say the total transfer length
> + * is 8KB, then max segments will still be 3(2,4,2) and not 4.
> + * 4 (read next higher value) segments will only be required
> + * once the length is at least 2 bytes more then 8KB (read any
> + * HV_HYP_PAGE_SIZE aligned length).
> */
> - host->sg_tablesize = (stor_device->max_transfer_bytes >> PAGE_SHIFT);
> + host->sg_tablesize = ((stor_device->max_transfer_bytes - 2) >> HV_HYP_PAGE_SHIFT) + 2;
> /*
> * For non-IDE disks, the host supports multiple channels.
> * Set the number of HW queues we are supporting.
> --
> 2.25.1
