From: Jianxin Xiong <jianxin.xiong@intel.com>
To: linux-rdma@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org
Cc: Jianxin Xiong <jianxin.xiong@intel.com>,
Doug Ledford <dledford@redhat.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
Christian Koenig <christian.koenig@amd.com>,
Daniel Vetter <daniel.vetter@intel.com>
Subject: [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned
Date: Wed, 14 Oct 2020 09:16:01 -0700 [thread overview]
Message-ID: <1602692161-107096-1-git-send-email-jianxin.xiong@intel.com> (raw)
The dma-buf API have been used under the assumption that the sg lists
returned from dma_buf_map_attachment() are fully page aligned. Lots of
stuff can break otherwise all over the place. Clarify this in the
documentation and add a check when DMA API debug is enabled.
Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
---
drivers/dma-buf/dma-buf.c | 21 +++++++++++++++++++++
include/linux/dma-buf.h | 3 ++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 844967f..7309c83 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -851,6 +851,9 @@ void dma_buf_unpin(struct dma_buf_attachment *attach)
* Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
* on error. May return -EINTR if it is interrupted by a signal.
*
+ * On success, the DMA addresses and lengths in the returned scatterlist are
+ * PAGE_SIZE aligned.
+ *
* A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
* the underlying backing storage is pinned for as long as a mapping exists,
* therefore users/importers should not hold onto a mapping for undue amounts of
@@ -904,6 +907,24 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
attach->dir = direction;
}
+#ifdef CONFIG_DMA_API_DEBUG
+ {
+ struct scatterlist *sg;
+ u64 addr;
+ int len;
+ int i;
+
+ for_each_sgtable_dma_sg(sg_table, sg, i) {
+ addr = sg_dma_address(sg);
+ len = sg_dma_len(sg);
+ if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
+ pr_debug("%s: addr %llx or len %x is not page aligned!\n",
+ __func__, addr, len);
+ }
+ }
+ }
+#endif /* CONFIG_DMA_API_DEBUG */
+
return sg_table;
}
EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index a2ca294e..4a5fa70 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -145,7 +145,8 @@ struct dma_buf_ops {
*
* A &sg_table scatter list of or the backing storage of the DMA buffer,
* already mapped into the device address space of the &device attached
- * with the provided &dma_buf_attachment.
+ * with the provided &dma_buf_attachment. The addresses and lengths in
+ * the scatter list are PAGE_SIZE aligned.
*
* On failure, returns a negative error value wrapped into a pointer.
* May also return -EINTR when a signal was received while being
--
1.8.3.1
next reply other threads:[~2020-10-14 16:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 16:16 Jianxin Xiong [this message]
2020-10-15 16:03 ` [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned Daniel Vetter
2020-10-15 16:31 ` Christian König
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