nvme: set dma alignment to qword

The default dma alignment mask is 511, which is much larger than any nvme
controller requires. NVMe controllers accept qword aligned DMA addresses,
so set the request_queue constraints to that. This can help avoid bounce
buffers on user passthrough commands.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index a3a4dbc59af18be0d20f4b3f7f066e4d3279cf14..569671e264b509157c512968265f9c87b5ad36d4 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2322,6 +2322,7 @@ static void nvme_set_queue_limits(struct nvme_ctrl *ctrl,
                blk_queue_max_segments(q, min_t(u32, max_segments, USHRT_MAX));
        }
        blk_queue_virt_boundary(q, ctrl->page_size - 1);
+       blk_queue_dma_alignment(q, 7);
        if (ctrl->vwc & NVME_CTRL_VWC_PRESENT)
                vwc = true;
        blk_queue_write_cache(q, vwc, vwc);