diff mbox series

[v6,1/2] habanalabs: define uAPI to export FD for DMA-BUF

Message ID 20210912165309.98695-2-ogabbay@kernel.org (mailing list archive)
State New, archived
Headers show
Series Add p2p via dmabuf to habanalabs | expand

Commit Message

Oded Gabbay Sept. 12, 2021, 4:53 p.m. UTC 
User process might want to share the device memory with another
driver/device, and to allow it to access it over PCIe (P2P).

To enable this, we utilize the dma-buf mechanism and add a dma-buf
exporter support, so the other driver can import the device memory and
access it.

The device memory is allocated using our existing allocation uAPI,
where the user will get a handle that represents the allocation.

The user will then need to call the new
uAPI (HL_MEM_OP_EXPORT_DMABUF_FD) and give the handle as a parameter.

The driver will return a FD that represents the DMA-BUF object that
was created to match that allocation.

Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Reviewed-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/uapi/misc/habanalabs.h | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

Comments

Jason Gunthorpe Sept. 28, 2021, 5:13 p.m. UTC | #1 
On Sun, Sep 12, 2021 at 07:53:08PM +0300, Oded Gabbay wrote:
>  	/* HL_MEM_OP_* */
>  	__u32 op;
> -	/* HL_MEM_* flags */
> +	/* HL_MEM_* flags.
> +	 * For the HL_MEM_OP_EXPORT_DMABUF_FD opcode, this field holds the
> +	 * DMA-BUF file/FD flags.
> +	 */
>  	__u32 flags;
>  	/* Context ID - Currently not in use */
>  	__u32 ctx_id;
> @@ -1072,6 +1091,13 @@ struct hl_mem_out {
>  
>  			__u32 pad;
>  		};
> +
> +		/* Returned in HL_MEM_OP_EXPORT_DMABUF_FD. Represents the
> +		 * DMA-BUF object that was created to describe a memory
> +		 * allocation on the device's memory space. The FD should be
> +		 * passed to the importer driver
> +		 */
> +		__u64 fd;

fd's should be a s32 type in a fixed width uapi.

I usually expect to see the uapi changes inside the commit that
consumes them, splitting the patch like this seems strange but
harmless.

Jason
Oded Gabbay Sept. 28, 2021, 7:12 p.m. UTC | #2 
On Tue, Sep 28, 2021 at 8:13 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Sun, Sep 12, 2021 at 07:53:08PM +0300, Oded Gabbay wrote:
> >       /* HL_MEM_OP_* */
> >       __u32 op;
> > -     /* HL_MEM_* flags */
> > +     /* HL_MEM_* flags.
> > +      * For the HL_MEM_OP_EXPORT_DMABUF_FD opcode, this field holds the
> > +      * DMA-BUF file/FD flags.
> > +      */
> >       __u32 flags;
> >       /* Context ID - Currently not in use */
> >       __u32 ctx_id;
> > @@ -1072,6 +1091,13 @@ struct hl_mem_out {
> >
> >                       __u32 pad;
> >               };
> > +
> > +             /* Returned in HL_MEM_OP_EXPORT_DMABUF_FD. Represents the
> > +              * DMA-BUF object that was created to describe a memory
> > +              * allocation on the device's memory space. The FD should be
> > +              * passed to the importer driver
> > +              */
> > +             __u64 fd;
>
> fd's should be a s32 type in a fixed width uapi.
Yep, will correct this.

>
> I usually expect to see the uapi changes inside the commit that
> consumes them, splitting the patch like this seems strange but
> harmless.
I'll remember that when I send the RDMA patches down the road :)

Thanks,
Oded
>
> Jason
diff mbox series

Patch

diff --git a/include/uapi/misc/habanalabs.h b/include/uapi/misc/habanalabs.h
index 042e96f99d85..b1def68bf5d3 100644
--- a/include/uapi/misc/habanalabs.h
+++ b/include/uapi/misc/habanalabs.h
@@ -960,6 +960,10 @@  union hl_wait_cs_args {
 #define HL_MEM_OP_UNMAP			3
 /* Opcode to map a hw block */
 #define HL_MEM_OP_MAP_BLOCK		4
+/* Opcode to create DMA-BUF object for an existing device memory allocation
+ * and to export an FD of that DMA-BUF back to the caller
+ */
+#define HL_MEM_OP_EXPORT_DMABUF_FD	5
 
 /* Memory flags */
 #define HL_MEM_CONTIGUOUS	0x1
@@ -1031,11 +1035,26 @@  struct hl_mem_in {
 			/* Virtual address returned from HL_MEM_OP_MAP */
 			__u64 device_virt_addr;
 		} unmap;
+
+		/* HL_MEM_OP_EXPORT_DMABUF_FD */
+		struct {
+			/* Handle returned from HL_MEM_OP_ALLOC. In Gaudi,
+			 * where we don't have MMU for the device memory, the
+			 * driver expects a physical address (instead of
+			 * a handle) in the device memory space.
+			 */
+			__u64 handle;
+			/* Size of memory allocation. Relevant only for GAUDI */
+			__u64 mem_size;
+		} export_dmabuf_fd;
 	};
 
 	/* HL_MEM_OP_* */
 	__u32 op;
-	/* HL_MEM_* flags */
+	/* HL_MEM_* flags.
+	 * For the HL_MEM_OP_EXPORT_DMABUF_FD opcode, this field holds the
+	 * DMA-BUF file/FD flags.
+	 */
 	__u32 flags;
 	/* Context ID - Currently not in use */
 	__u32 ctx_id;
@@ -1072,6 +1091,13 @@  struct hl_mem_out {
 
 			__u32 pad;
 		};
+
+		/* Returned in HL_MEM_OP_EXPORT_DMABUF_FD. Represents the
+		 * DMA-BUF object that was created to describe a memory
+		 * allocation on the device's memory space. The FD should be
+		 * passed to the importer driver
+		 */
+		__u64 fd;
 	};
 };