From: Christoph Hellwig <hch@lst.de>
To: Sebastian Ott <sebott@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>, Ming Lei <ming.lei@redhat.com>,
Hannes Reinecke <hare@suse.com>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: too large sg segments with commit 09324d32d2a08
Date: Wed, 5 Jun 2019 15:30:02 +0200 [thread overview]
Message-ID: <20190605133002.GA13368@lst.de> (raw)
In-Reply-To: <20190605100928.GA9828@lst.de>
Actually, it looks like something completely general isn't
easily doable, not without some major dma API work. Here is what
should fix nvme, but a few other drivers will need fixes as well:
---
From 745541130409bc837a3416300f529b16eded8513 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 5 Jun 2019 14:55:26 +0200
Subject: nvme-pci: don't limit DMA segement size
NVMe uses PRPs (or optionally unlimited SGLs) for data transfers and
has no specific limit for a single DMA segement. Limiting the size
will cause problems because the block layer assumes PRP-ish devices
using a virt boundary mask don't have a segment limit. And while this
is true, we also really need to tell the DMA mapping layer about it,
otherwise dma-debug will trip over it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Sebastian Ott <sebott@linux.ibm.com>
---
drivers/nvme/host/pci.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index f562154551ce..524d6bd6d095 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2513,6 +2513,12 @@ static void nvme_reset_work(struct work_struct *work)
*/
dev->ctrl.max_hw_sectors = NVME_MAX_KB_SZ << 1;
dev->ctrl.max_segments = NVME_MAX_SEGS;
+
+ /*
+ * Don't limit the IOMMU merged segment size.
+ */
+ dma_set_max_seg_size(dev->dev, 0xffffffff);
+
mutex_unlock(&dev->shutdown_lock);
/*
--
2.20.1
next prev parent reply other threads:[~2019-06-05 13:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 9:13 too large sg segments with commit 09324d32d2a08 Sebastian Ott
2019-06-05 10:09 ` Christoph Hellwig
2019-06-05 13:30 ` Christoph Hellwig [this message]
2019-06-05 13:57 ` Sebastian Ott
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