[PATCH 28/33] scsi: qla2xxx: Use coherent DMA buffer for D_Port diagnostics

qla26xx_dport_diagnostics() streaming-maps the caller's result buffer with
dma_map_single(). The bsg path passes &dd->buf from the __packed struct
qla_dport_diag, where buf lands at a 2-byte offset and shares cachelines
with the surrounding options/unused fields. Mapping such a misaligned
sub-buffer violates the DMA API requirement that streaming buffers be
cacheline aligned and not share a cacheline with other data, and can
corrupt data on non-DMA-coherent architectures.

Allocate a dedicated DMA-coherent buffer inside qla26xx_dport_diagnostics()
for the mailbox command and copy the result back into the caller's buffer.
This removes the streaming map of the misaligned sub-buffer entirely; the
caller's buffer is now only a plain CPU buffer, so its packing no longer
matters.

Fixes: ec89146215d1 ("qla2xxx: Add bsg interface to support D_Port Diagnostics.")
Cc: [email protected]
Reported-by: Sashiko <[email protected]>
Signed-off-by: Nilesh Javali <[email protected]>
---
 drivers/scsi/qla2xxx/qla_mbx.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/qla2xxx/qla_mbx.c b/drivers/scsi/qla2xxx/qla_mbx.c
index 39544deab576..59ec5605930b 100644
--- a/drivers/scsi/qla2xxx/qla_mbx.c
+++ b/drivers/scsi/qla2xxx/qla_mbx.c
@@ -6579,6 +6579,7 @@ qla26xx_dport_diagnostics(scsi_qla_host_t *vha,
 	mbx_cmd_t mc;
 	mbx_cmd_t *mcp = &mc;
 	dma_addr_t dd_dma;
+	void *dd;
 
 	if (!IS_QLA83XX(vha->hw) && !IS_QLA27XX(vha->hw) &&
 	    !IS_QLA28XX(vha->hw) && !IS_QLA29XX(vha->hw))
@@ -6587,15 +6588,12 @@ qla26xx_dport_diagnostics(scsi_qla_host_t *vha,
 	ql_dbg(ql_dbg_mbx + ql_dbg_verbose, vha, 0x119f,
 	    "Entered %s.\n", __func__);
 
-	dd_dma = dma_map_single(&vha->hw->pdev->dev,
-	    dd_buf, size, DMA_FROM_DEVICE);
-	if (dma_mapping_error(&vha->hw->pdev->dev, dd_dma)) {
-		ql_log(ql_log_warn, vha, 0x1194, "Failed to map dma buffer.\n");
+	dd = dma_alloc_coherent(&vha->hw->pdev->dev, size, &dd_dma, GFP_KERNEL);
+	if (!dd) {
+		ql_log(ql_log_warn, vha, 0x1194, "Failed to allocate dma buffer.\n");
 		return QLA_MEMORY_ALLOC_FAILED;
 	}
 
-	memset(dd_buf, 0, size);
-
 	mcp->mb[0] = MBC_DPORT_DIAGNOSTICS;
 	mcp->mb[1] = options;
 	mcp->mb[2] = MSW(LSD(dd_dma));
@@ -6617,8 +6615,9 @@ qla26xx_dport_diagnostics(scsi_qla_host_t *vha,
 		    "Done %s.\n", __func__);
 	}
 
-	dma_unmap_single(&vha->hw->pdev->dev, dd_dma,
-	    size, DMA_FROM_DEVICE);
+	memcpy(dd_buf, dd, size);
+
+	dma_free_coherent(&vha->hw->pdev->dev, size, dd, dd_dma);
 
 	return rval;
 }
-- 
2.47.3