[RFC PATCH v3 12/20] io_uring: add ZC buf and pool

David Wei
2023-12-19T21:04:16Z

From: David Wei <davidhwei@meta.com>

[TODO: REVIEW COMMIT MESSAGE]

This patch adds two objects:

* Zero copy buffer representation, holding a page, its mapped dma_addr,
and a refcount for lifetime management.
* Zero copy pool, spiritually similar to page pool, that holds ZC bufs
and hands them out to net devices.

Pool regions are registered w/ io_uring using the registered buffer API,
with a 1:1 mapping between region and nr_iovec in
io_uring_register_buffers. This does the heavy lifting of pinning and
chunking into bvecs into a struct io_mapped_ubuf for us.

For now as there is only one pool region per ifq, there is no separate
API for adding/removing regions yet and it is mapped implicitly during
ifq registration.

Signed-off-by: David Wei <dw@davidwei.uk>
---
include/linux/io_uring/net.h | 8 +++
io_uring/zc_rx.c | 135 ++++++++++++++++++++++++++++++++++-
io_uring/zc_rx.h | 15 ++++
3 files changed, 157 insertions(+), 1 deletion(-)

diff --git a/include/linux/io_uring/net.h b/include/linux/io_uring/net.h
index b58f39fed4d5..d994d26116d0 100644
--- a/include/linux/io_uring/net.h
+++ b/include/linux/io_uring/net.h
@@ -2,8 +2,16 @@
#ifndef _LINUX_IO_URING_NET_H
#define _LINUX_IO_URING_NET_H

+#include <net/page_pool/types.h>
+
struct io_uring_cmd;

+struct io_zc_rx_buf {
+ struct page_pool_iov ppiov;
+ struct page *page;
+ dma_addr_t dma;
+};
+
#if defined(CONFIG_IO_URING)
int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags);

diff --git a/io_uring/zc_rx.c b/io_uring/zc_rx.c
index 06e2c54d3f3d..1e656b481725 100644
--- a/io_uring/zc_rx.c
+++ b/io_uring/zc_rx.c
@@ -5,6 +5,7 @@
#include <linux/mm.h>
#include <linux/io_uring.h>
#include <linux/netdevice.h>
+#include <linux/nospec.h>

#include <uapi/linux/io_uring.h>

@@ -15,6 +16,11 @@

typedef int (*bpf_op_t)(struct net_device *dev, struct netdev_bpf *bpf);

+static inline struct device *netdev2dev(struct net_device *dev)
+{
+ return dev->dev.parent;
+}
+
static int __io_queue_mgmt(struct net_device *dev, struct io_zc_rx_ifq *ifq,
u16 queue_id)
{
@@ -67,6 +73,129 @@ static void io_free_rbuf_ring(struct io_zc_rx_ifq *ifq)
folio_put(virt_to_folio(ifq->ring));
}

+static int io_zc_rx_init_buf(struct device *dev, struct page *page, u16 pool_id,
+ u32 pgid, struct io_zc_rx_buf *buf)
+{
+ dma_addr_t addr = 0;
+
+ /* Skip dma setup for devices that don't do any DMA transfers */
+ if (dev) {
+ addr = dma_map_page_attrs(dev, page, 0, PAGE_SIZE,
+ DMA_BIDIRECTIONAL,
+ DMA_ATTR_SKIP_CPU_SYNC);
+ if (dma_mapping_error(dev, addr))
+ return -ENOMEM;
+ }
+
+ buf->dma = addr;
+ buf->page = page;
+ refcount_set(&buf->ppiov.refcount, 0);
+ buf->ppiov.owner = NULL;
+ buf->ppiov.pp = NULL;
+ get_page(page);
+ return 0;
+}
+
+static void io_zc_rx_free_buf(struct device *dev, struct io_zc_rx_buf *buf)
+{
+ struct page *page = buf->page;
+
+ if (dev)
+ dma_unmap_page_attrs(dev, buf->dma, PAGE_SIZE,
+ DMA_BIDIRECTIONAL,
+ DMA_ATTR_SKIP_CPU_SYNC);
+ put_page(page);
+}
+
+static int io_zc_rx_map_pool(struct io_zc_rx_pool *pool,
+ struct io_mapped_ubuf *imu,
+ struct device *dev)
+{
+ struct io_zc_rx_buf *buf;
+ struct page *page;
+ int i, ret;
+
+ for (i = 0; i < imu->nr_bvecs; i++) {
+ page = imu->bvec[i].bv_page;
+ buf = &pool->bufs[i];
+ ret = io_zc_rx_init_buf(dev, page, pool->pool_id, i, buf);
+ if (ret)
+ goto err;
+
+ pool->freelist[i] = i;
+ }
+
+ pool->free_count = imu->nr_bvecs;
+ return 0;
+err:
+ while (i--) {
+ buf = &pool->bufs[i];
+ io_zc_rx_free_buf(dev, buf);
+ }
+ return ret;
+}
+
+static int io_zc_rx_create_pool(struct io_ring_ctx *ctx,
+ struct io_zc_rx_ifq *ifq,
+ u16 id)
+{
+ struct device *dev = netdev2dev(ifq->dev);
+ struct io_mapped_ubuf *imu;
+ struct io_zc_rx_pool *pool;
+ int nr_pages;
+ int ret;
+
+ if (ifq->pool)
+ return -EFAULT;
+
+ if (unlikely(id >= ctx->nr_user_bufs))
+ return -EFAULT;
+ id = array_index_nospec(id, ctx->nr_user_bufs);
+ imu = ctx->user_bufs[id];
+ if (imu->ubuf & ~PAGE_MASK || imu->ubuf_end & ~PAGE_MASK)
+ return -EFAULT;
+
+ ret = -ENOMEM;
+ nr_pages = imu->nr_bvecs;
+ pool = kvmalloc(struct_size(pool, freelist, nr_pages), GFP_KERNEL);
+ if (!pool)
+ goto err;
+
+ pool->bufs = kvmalloc_array(nr_pages, sizeof(*pool->bufs), GFP_KERNEL);
+ if (!pool->bufs)
+ goto err_buf;
+
+ ret = io_zc_rx_map_pool(pool, imu, dev);
+ if (ret)
+ goto err_map;
+
+ pool->ifq = ifq;
+ pool->pool_id = id;
+ pool->nr_bufs = nr_pages;
+ spin_lock_init(&pool->freelist_lock);
+ ifq->pool = pool;
+ return 0;
+err_map:
+ kvfree(pool->bufs);
+err_buf:
+ kvfree(pool);
+err:
+ return ret;
+}
+
+static void io_zc_rx_destroy_pool(struct io_zc_rx_pool *pool)
+{
+ struct device *dev = netdev2dev(pool->ifq->dev);
+ struct io_zc_rx_buf *buf;
+
+ for (int i = 0; i < pool->nr_bufs; i++) {
+ buf = &pool->bufs[i];
+ io_zc_rx_free_buf(dev, buf);
+ }
+ kvfree(pool->bufs);
+ kvfree(pool);
+}
+
static struct io_zc_rx_ifq *io_zc_rx_ifq_alloc(struct io_ring_ctx *ctx)
{
struct io_zc_rx_ifq *ifq;
@@ -105,6 +234,8 @@ static void io_zc_rx_ifq_free(struct io_zc_rx_ifq *ifq)
{
io_shutdown_ifq(ifq);

+ if (ifq->pool)
+ io_zc_rx_destroy_pool(ifq->pool);
if (ifq->dev)
dev_put(ifq->dev);
io_free_rbuf_ring(ifq);
@@ -141,7 +272,9 @@ int io_register_zc_rx_ifq(struct io_ring_ctx *ctx,
if (!ifq->dev)
goto err;

- /* TODO: map zc region and initialise zc pool */
+ ret = io_zc_rx_create_pool(ctx, ifq, reg.region_id);
+ if (ret)
+ goto err;

ifq->rq_entries = reg.rq_entries;
ifq->cq_entries = reg.cq_entries;
diff --git a/io_uring/zc_rx.h b/io_uring/zc_rx.h
index 9257dda77e92..af1d865525d2 100644
--- a/io_uring/zc_rx.h
+++ b/io_uring/zc_rx.h
@@ -3,15 +3,30 @@
#define IOU_ZC_RX_H

#include <linux/io_uring_types.h>
+#include <linux/io_uring/net.h>
#include <linux/skbuff.h>

#define IO_ZC_MAX_IFQ_SOCKETS 16
#define IO_ZC_IFQ_IDX_OFFSET 16
#define IO_ZC_IFQ_IDX_MASK ((1U << IO_ZC_IFQ_IDX_OFFSET) - 1)

+struct io_zc_rx_pool {
+ struct io_zc_rx_ifq *ifq;
+ struct io_zc_rx_buf *bufs;
+ u32 nr_bufs;
+ u16 pool_id;
+
+ /* freelist */
+ spinlock_t freelist_lock;
+ u32 free_count;
+ u32 freelist[];
+};
+
struct io_zc_rx_ifq {
struct io_ring_ctx *ctx;
struct net_device *dev;
+ struct io_zc_rx_pool *pool;
+
struct io_rbuf_ring *ring;
struct io_uring_rbuf_rqe *rqes;
struct io_uring_rbuf_cqe *cqes;
--
2.39.3