* [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned
@ 2020-10-14 16:16 Jianxin Xiong
2020-10-15 16:03 ` Daniel Vetter
0 siblings, 1 reply; 3+ messages in thread
From: Jianxin Xiong @ 2020-10-14 16:16 UTC (permalink / raw)
To: linux-rdma, dri-devel, linux-media, linaro-mm-sig
Cc: Jianxin Xiong, Doug Ledford, Jason Gunthorpe, Leon Romanovsky,
Sumit Semwal, Christian Koenig, Daniel Vetter
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned
2020-10-14 16:16 [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned Jianxin Xiong
@ 2020-10-15 16:03 ` Daniel Vetter
2020-10-15 16:31 ` Christian König
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Vetter @ 2020-10-15 16:03 UTC (permalink / raw)
To: Jianxin Xiong
Cc: linux-rdma, dri-devel, linux-media, linaro-mm-sig,
Leon Romanovsky, Jason Gunthorpe, Doug Ledford, Daniel Vetter,
Christian Koenig
On Wed, Oct 14, 2020 at 09:16:01AM -0700, Jianxin Xiong wrote:
> 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>
lgtm, thanks for creating this and giving it a spin.
I'll queue this up in drm-misc-next for 5.11, should show up in linux-next
after the merge window is closed.
Cheers, Daniel
> ---
> 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
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned
2020-10-15 16:03 ` Daniel Vetter
@ 2020-10-15 16:31 ` Christian König
0 siblings, 0 replies; 3+ messages in thread
From: Christian König @ 2020-10-15 16:31 UTC (permalink / raw)
To: Daniel Vetter, Jianxin Xiong
Cc: linux-rdma, dri-devel, linux-media, linaro-mm-sig,
Leon Romanovsky, Jason Gunthorpe, Doug Ledford, Daniel Vetter
Am 15.10.20 um 18:03 schrieb Daniel Vetter:
> On Wed, Oct 14, 2020 at 09:16:01AM -0700, Jianxin Xiong wrote:
>> 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>
Reviewed-by: Christian König <christian.koenig@amd.com>
> lgtm, thanks for creating this and giving it a spin.
>
> I'll queue this up in drm-misc-next for 5.11, should show up in linux-next
> after the merge window is closed.
Thanks, I'm currently without landline internet and need to rely on my
mobile.
Christian.
>
> Cheers, Daniel
>
>> ---
>> 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
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel&data=04%7C01%7Cchristian.koenig%40amd.com%7C58ee8712041e4e742fe408d87123e970%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637383746351346603%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=EwAEVcJa6gboHMEQ6XUymC%2BtjFoWd0wl8YUyzdnV5N8%3D&reserved=0
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2020-10-14 16:16 [PATCH v4 5/5] dma-buf: Clarify that dma-buf sg lists are page aligned Jianxin Xiong
2020-10-15 16:03 ` Daniel Vetter
2020-10-15 16:31 ` Christian König
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