From 176ddd89171ddcf661862d90c5d257877f7326d6 Mon Sep 17 00:00:00 2001 From: Jolly Shah Date: Thu, 18 Mar 2021 15:56:32 -0700 Subject: [PATCH] scsi: libsas: Reset num_scatter if libata marks qc as NODATA When the cache_type for the SCSI device is changed, the SCSI layer issues a MODE_SELECT command. The caching mode details are communicated via a request buffer associated with the SCSI command with data direction set as DMA_TO_DEVICE (scsi_mode_select()). When this command reaches the libata layer, as a part of generic initial setup, libata layer sets up the scatterlist for the command using the SCSI command (ata_scsi_qc_new()). This command is then translated by the libata layer into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat()). The libata layer treats this as a non-data command (ata_mselect_caching()), since it only needs an ATA taskfile to pass the caching on/off information to the device. It does not need the scatterlist that has been setup, so it does not perform dma_map_sg() on the scatterlist (ata_qc_issue()). Unfortunately, when this command reaches the libsas layer (sas_ata_qc_issue()), libsas layer sees it as a non-data command with a scatterlist. It cannot extract the correct DMA length since the scatterlist has not been mapped with dma_map_sg() for a DMA operation. When this partially constructed SAS task reaches pm80xx LLDD, it results in the following warning: "pm80xx_chip_sata_req 6058: The sg list address start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff end_addr_low=0xffffffff has crossed 4G boundary" Update libsas to handle ATA non-data commands separately so num_scatter and total_xfer_len remain 0. Link: https://lore.kernel.org/r/20210318225632.2481291-1-jollys@google.com Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA") Tested-by: Luo Jiaxing Reviewed-by: John Garry Signed-off-by: Jolly Shah Signed-off-by: Martin K. Petersen --- drivers/scsi/libsas/sas_ata.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c index 024e5a5..8b9a390 100644 --- a/drivers/scsi/libsas/sas_ata.c +++ b/drivers/scsi/libsas/sas_ata.c @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc) memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len); task->total_xfer_len = qc->nbytes; task->num_scatter = qc->n_elem; + task->data_dir = qc->dma_dir; + } else if (qc->tf.protocol == ATA_PROT_NODATA) { + task->data_dir = DMA_NONE; } else { for_each_sg(qc->sg, sg, qc->n_elem, si) xfer += sg_dma_len(sg); task->total_xfer_len = xfer; task->num_scatter = si; - } - - if (qc->tf.protocol == ATA_PROT_NODATA) - task->data_dir = DMA_NONE; - else task->data_dir = qc->dma_dir; + } task->scatter = qc->sg; task->ata_task.retry_count = 1; task->task_state_flags = SAS_TASK_STATE_PENDING; -- 2.7.4