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From: Keith Busch <kbusch@kernel.org>
To: linux-nvme@lists.infradead.org, hch@lst.de, sagi@grimberg.me
Cc: Keith Busch <kbusch@kernel.org>
Subject: [PATCH] nvme: set dma alignment to qword
Date: Wed, 20 May 2020 19:22:53 -0700	[thread overview]
Message-ID: <20200521022253.3268324-1-kbusch@kernel.org> (raw)

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>
---
 drivers/nvme/host/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 805d289e6cd9..ba860efd250d 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2283,6 +2283,7 @@ 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);
-- 
2.24.1


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             reply	other threads:[~2020-05-21  2:23 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21  2:22 Keith Busch [this message]
2020-05-21  6:05 ` [PATCH] nvme: set dma alignment to qword Sagi Grimberg
2020-05-21 15:28   ` Keith Busch
2020-05-21 15:29     ` Christoph Hellwig
2020-05-21 15:41       ` Keith Busch
2020-05-21 15:42         ` Christoph Hellwig
2020-05-21 19:46           ` James Smart
2020-05-26 14:53 ` Christoph Hellwig

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