[bpf-next V5 PATCH 02/15] xdp: introduce xdp_return_frame API and use in cpumap

Jesper Dangaard Brouer
2018-03-23T12:18:13Z

Introduce an xdp_return_frame API, and convert over cpumap as
the first user, given it have queued XDP frame structure to leverage.

V3: Cleanup and remove C99 style comments, pointed out by Alex Duyck.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/xdp.h | 28 ++++++++++++++++++++++++
kernel/bpf/cpumap.c | 60 +++++++++++++++++++++++++++++++--------------------
net/core/xdp.c | 18 +++++++++++++++
3 files changed, 82 insertions(+), 24 deletions(-)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index b2362ddfa694..15b546325e31 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -33,16 +33,44 @@
* also mandatory during RX-ring setup.
*/

+enum mem_type {
+ MEM_TYPE_PAGE_SHARED = 0, /* Split-page refcnt based model */
+ MEM_TYPE_PAGE_ORDER0, /* Orig XDP full page model */
+ MEM_TYPE_MAX,
+};
+
+struct xdp_mem_info {
+ u32 type; /* enum mem_type, but known size type */
+ /* u32 id; will be added later in this patchset */
+};
+
struct xdp_rxq_info {
struct net_device *dev;
u32 queue_index;
u32 reg_state;
+ struct xdp_mem_info mem;
} ____cacheline_aligned; /* perf critical, avoid false-sharing */

+
+static inline
+void xdp_return_frame(void *data, struct xdp_mem_info *mem)
+{
+ if (mem->type == MEM_TYPE_PAGE_SHARED)
+ page_frag_free(data);
+
+ if (mem->type == MEM_TYPE_PAGE_ORDER0) {
+ struct page *page = virt_to_page(data); /* Assumes order0 page*/
+
+ put_page(page);
+ }
+}
+
int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
struct net_device *dev, u32 queue_index);
void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq);
void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq);
bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq);
+int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
+ enum mem_type type, void *allocator);

#endif /* __LINUX_NET_XDP_H__ */
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index a4bb0b34375a..3e4bbcbe3e86 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -19,6 +19,7 @@
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/ptr_ring.h>
+#include <net/xdp.h>

#include <linux/sched.h>
#include <linux/workqueue.h>
@@ -137,27 +138,6 @@ static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
return ERR_PTR(err);
}

-static void __cpu_map_queue_destructor(void *ptr)
-{
- /* The tear-down procedure should have made sure that queue is
- * empty. See __cpu_map_entry_replace() and work-queue
- * invoked cpu_map_kthread_stop(). Catch any broken behaviour
- * gracefully and warn once.
- */
- if (WARN_ON_ONCE(ptr))
- page_frag_free(ptr);
-}
-
-static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
-{
- if (atomic_dec_and_test(&rcpu->refcnt)) {
- /* The queue should be empty at this point */
- ptr_ring_cleanup(rcpu->queue, __cpu_map_queue_destructor);
- kfree(rcpu->queue);
- kfree(rcpu);
- }
-}
-
static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
{
atomic_inc(&rcpu->refcnt);
@@ -188,6 +168,10 @@ struct xdp_pkt {
u16 len;
u16 headroom;
u16 metasize;
+ /* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time,
+ * while mem info is valid on remote CPU.
+ */
+ struct xdp_mem_info mem;
struct net_device *dev_rx;
};

@@ -213,6 +197,9 @@ static struct xdp_pkt *convert_to_xdp_pkt(struct xdp_buff *xdp)
xdp_pkt->headroom = headroom - sizeof(*xdp_pkt);
xdp_pkt->metasize = metasize;

+ /* rxq only valid until napi_schedule ends, convert to xdp_mem_info */
+ xdp_pkt->mem = xdp->rxq->mem;
+
return xdp_pkt;
}

@@ -265,6 +252,31 @@ static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
return skb;
}

+static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
+{
+ /* The tear-down procedure should have made sure that queue is
+ * empty. See __cpu_map_entry_replace() and work-queue
+ * invoked cpu_map_kthread_stop(). Catch any broken behaviour
+ * gracefully and warn once.
+ */
+ struct xdp_pkt *xdp_pkt;
+
+ while ((xdp_pkt = ptr_ring_consume(ring)))
+ if (WARN_ON_ONCE(xdp_pkt))
+ xdp_return_frame(xdp_pkt, &xdp_pkt->mem);
+}
+
+static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
+{
+ if (atomic_dec_and_test(&rcpu->refcnt)) {
+ /* The queue should be empty at this point */
+ __cpu_map_ring_cleanup(rcpu->queue);
+ ptr_ring_cleanup(rcpu->queue, NULL);
+ kfree(rcpu->queue);
+ kfree(rcpu);
+ }
+}
+
static int cpu_map_kthread_run(void *data)
{
struct bpf_cpu_map_entry *rcpu = data;
@@ -307,7 +319,7 @@ static int cpu_map_kthread_run(void *data)

skb = cpu_map_build_skb(rcpu, xdp_pkt);
if (!skb) {
- page_frag_free(xdp_pkt);
+ xdp_return_frame(xdp_pkt, &xdp_pkt->mem);
continue;
}

@@ -604,13 +616,13 @@ static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
spin_lock(&q->producer_lock);

for (i = 0; i < bq->count; i++) {
- void *xdp_pkt = bq->q[i];
+ struct xdp_pkt *xdp_pkt = bq->q[i];
int err;

err = __ptr_ring_produce(q, xdp_pkt);
if (err) {
drops++;
- page_frag_free(xdp_pkt); /* Free xdp_pkt */
+ xdp_return_frame(xdp_pkt->data, &xdp_pkt->mem);
}
processed++;
}
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 097a0f74e004..9eee0c431126 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -71,3 +71,21 @@ bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq)
return (xdp_rxq->reg_state == REG_STATE_REGISTERED);
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_is_reg);
+
+int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
+ enum mem_type type, void *allocator)
+{
+ if (type >= MEM_TYPE_MAX)
+ return -EINVAL;
+
+ xdp_rxq->mem.type = type;
+
+ if (allocator)
+ return -EOPNOTSUPP;
+
+ /* TODO: Allocate an ID that maps to allocator pointer
+ * See: https://www.kernel.org/doc/html/latest/core-api/idr.html
+ */
+ return 0;
+}
+EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);