diff mbox series

[v1,06/15] io_uring: Provide driver API for zctap packet buffers.

Message ID 20221108050521.3198458-7-jonathan.lemon@gmail.com (mailing list archive)
State New
Headers show
Series zero-copy RX for io_uring | expand

Commit Message

Jonathan Lemon Nov. 8, 2022, 5:05 a.m. UTC 
Introduce 'struct io_zctap_buf', representing a buffer used by
the network drivers, and the get/put functions which are used
by the network driver to obtain the buffers.

The code for these will be fleshed out in a following patch.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
---
 include/linux/io_uring.h | 47 ++++++++++++++++++++++++++++++++++++++++
 io_uring/zctap.c         | 23 ++++++++++++++++++++
 2 files changed, 70 insertions(+)

Comments

Christoph Hellwig Nov. 16, 2022, 8:17 a.m. UTC | #1 
On Mon, Nov 07, 2022 at 09:05:12PM -0800, Jonathan Lemon wrote:
> +struct io_zctap_buf *io_zctap_get_buf(struct io_zctap_ifq *ifq, int refc)
> +{
> +	return NULL;
> +}
> +EXPORT_SYMBOL(io_zctap_get_buf);
> +
> +void io_zctap_put_buf(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf)
> +{
> +}
> +EXPORT_SYMBOL(io_zctap_put_buf);

Adding stubs without anything in them is rather pointless.

Also why are these exported?  I can't find any modular users anywhere.
Even if so, any low-level uring zero copy functionality should be
EXPORT_SYMBOL_GPL, and only added once the modular users show up and
are discussed.
Jonathan Lemon Nov. 17, 2022, 9:01 p.m. UTC | #2 
On 16 Nov 2022, at 0:17, Christoph Hellwig wrote:

> On Mon, Nov 07, 2022 at 09:05:12PM -0800, Jonathan Lemon wrote:
>> +struct io_zctap_buf *io_zctap_get_buf(struct io_zctap_ifq *ifq, int refc)
>> +{
>> +	return NULL;
>> +}
>> +EXPORT_SYMBOL(io_zctap_get_buf);
>> +
>> +void io_zctap_put_buf(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf)
>> +{
>> +}
>> +EXPORT_SYMBOL(io_zctap_put_buf);
>
> Adding stubs without anything in them is rather pointless.

This patch just introduces the API, for easier reviewing (and handling
some patch dependencies).  Patch 8 adds the initial implementation.


> Also why are these exported?  I can't find any modular users anywhere.
> Even if so, any low-level uring zero copy functionality should be
> EXPORT_SYMBOL_GPL, and only added once the modular users show up and
> are discussed.

I just copied EXPORT_SYMBOL from io_uring.c, and have no preference
as to which export variant is used.

I was testing against several drivers, which were loadable modules for
ease of development.  For example, Broadcom’s in-tree bnxt driver does not
(currently) have steering support, so testing was against their external
driver package while waiting for the features to land upstream.
diff mbox series

Patch

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 43bc8a2edccf..97c1a2e37077 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -32,6 +32,13 @@  struct io_uring_cmd {
 	u8		pdu[32]; /* available inline for free use */
 };
 
+struct io_zctap_buf {
+	dma_addr_t	dma;
+	struct page	*page;
+	atomic_t	refcount;
+	u8		_pad[4];
+};
+
 #if defined(CONFIG_IO_URING)
 int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter, void *ioucmd);
@@ -44,6 +51,21 @@  void __io_uring_free(struct task_struct *tsk);
 void io_uring_unreg_ringfd(void);
 const char *io_uring_get_opcode(u8 opcode);
 
+struct io_zctap_ifq;
+struct io_zctap_buf *io_zctap_get_buf(struct io_zctap_ifq *ifq, int refc);
+void io_zctap_put_buf(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf);
+void io_zctap_put_buf_refs(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf,
+			   unsigned count);
+bool io_zctap_put_page(struct io_zctap_ifq *ifq, struct page *page);
+
+static inline dma_addr_t io_zctap_buf_dma(struct io_zctap_buf *buf)
+{
+	return buf->dma;
+}
+static inline struct page *io_zctap_buf_page(struct io_zctap_buf *buf)
+{
+	return buf->page;
+}
 static inline void io_uring_files_cancel(void)
 {
 	if (current->io_uring) {
@@ -92,6 +114,31 @@  static inline const char *io_uring_get_opcode(u8 opcode)
 {
 	return "";
 }
+static inline dma_addr_t io_zctap_buf_dma(struct io_zctap_buf *buf)
+{
+	return 0;
+}
+static inline struct page *io_zctap_buf_page(struct io_zctap_buf *buf)
+{
+	return NULL;
+}
+static inline struct io_zctap_buf *io_zctap_get_buf(struct io_zctap_ifq *ifq,
+						    int refc)
+{
+	return NULL;
+}
+void io_zctap_put_buf(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf)
+{
+}
+void io_zctap_put_buf_refs(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf,
+			   unsigned count)
+{
+}
+bool io_zctap_put_page(struct io_zctap_ifq *ifq, struct page *page)
+{
+	return false;
+}
+
 #endif
 
 #endif
diff --git a/io_uring/zctap.c b/io_uring/zctap.c
index 7426feee1e04..69a04de87f8f 100644
--- a/io_uring/zctap.c
+++ b/io_uring/zctap.c
@@ -37,6 +37,29 @@  static u64 zctap_mk_page_info(u16 region_id, u16 pgid)
 	return (u64)0xface << 48 | (u64)region_id << 16 | (u64)pgid;
 }
 
+struct io_zctap_buf *io_zctap_get_buf(struct io_zctap_ifq *ifq, int refc)
+{
+	return NULL;
+}
+EXPORT_SYMBOL(io_zctap_get_buf);
+
+void io_zctap_put_buf(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf)
+{
+}
+EXPORT_SYMBOL(io_zctap_put_buf);
+
+void io_zctap_put_buf_refs(struct io_zctap_ifq *ifq, struct io_zctap_buf *buf,
+			   unsigned count)
+{
+}
+EXPORT_SYMBOL(io_zctap_put_buf_refs);
+
+bool io_zctap_put_page(struct io_zctap_ifq *ifq, struct page *page)
+{
+	return false;
+}
+EXPORT_SYMBOL(io_zctap_put_page);
+
 static void io_remove_ifq_region(struct ifq_region *ifr)
 {
 	struct io_mapped_ubuf *imu;