(Minor changes requested below)
On 07/09/2021 14.35, Lorenzo Bianconi wrote:
Introduce flags field in xdp_frame and xdp_buffer data structures
to define additional buffer features. At the moment the only
supported buffer feature is multi-buffer bit (mb). Multi-buffer bit
is used to specify if this is a linear buffer (mb = 0) or a multi-buffer
frame (mb = 1). In the latter case the driver is expected to initialize
the skb_shared_info structure at the end of the first buffer to link
together subsequent buffers belonging to the same frame.
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
include/net/xdp.h | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/include/net/xdp.h b/include/net/xdp.h
index ad5b02dcb6f4..ed5ea784fd45 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -66,6 +66,10 @@ struct xdp_txq_info {
struct net_device *dev;
};
+enum xdp_buff_flags {
+ XDP_FLAGS_MULTI_BUFF = BIT(0), /* non-linear xdp buff */
+};
+
struct xdp_buff {
void *data;
void *data_end;
@@ -74,13 +78,30 @@ struct xdp_buff {
struct xdp_rxq_info *rxq;
struct xdp_txq_info *txq;
u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
+ u16 flags; /* supported values defined in xdp_flags */
^^^^^^^^^
Variable/enum is named "xdp_buff_flags", but comment says "xdp_flags".
I think we should change flags to use u32, because xdp_buff already
contain 4 byte padding. (pahole output provided as help below)
};
+static __always_inline bool xdp_buff_is_mb(struct xdp_buff *xdp)
+{
+ return !!(xdp->flags & XDP_FLAGS_MULTI_BUFF);
+}
+
+static __always_inline void xdp_buff_set_mb(struct xdp_buff *xdp)
+{
+ xdp->flags |= XDP_FLAGS_MULTI_BUFF;
+}
+
+static __always_inline void xdp_buff_clear_mb(struct xdp_buff *xdp)
+{
+ xdp->flags &= ~XDP_FLAGS_MULTI_BUFF;
+}
+
static __always_inline void
xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
{
xdp->frame_sz = frame_sz;
xdp->rxq = rxq;
+ xdp->flags = 0;
}
static __always_inline void
@@ -122,8 +143,14 @@ struct xdp_frame {
*/
struct xdp_mem_info mem;
struct net_device *dev_rx; /* used by cpumap */
+ u16 flags; /* supported values defined in xdp_flags */
^^^^^^^^^
Variable/enum is named "xdp_buff_flags", but comment says "xdp_flags".
Here (for xdp_frame) I also think we should change flags to u32, because
adding this u16 cause extra padding anyhow. (pahole output provided as
help below).
};
+static __always_inline bool xdp_frame_is_mb(struct xdp_frame *frame)
+{
+ return !!(frame->flags & XDP_FLAGS_MULTI_BUFF);
+}
+
#define XDP_BULK_QUEUE_SIZE 16
struct xdp_frame_bulk {
int count;
@@ -180,6 +207,7 @@ void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
xdp->data_end = frame->data + frame->len;
xdp->data_meta = frame->data - frame->metasize;
xdp->frame_sz = frame->frame_sz;
+ xdp->flags = frame->flags;
}
static inline
@@ -206,6 +234,7 @@ int xdp_update_frame_from_buff(struct xdp_buff *xdp,
xdp_frame->headroom = headroom - sizeof(*xdp_frame);
xdp_frame->metasize = metasize;
xdp_frame->frame_sz = xdp->frame_sz;
+ xdp_frame->flags = xdp->flags;
return 0;
}
Details below... no need to read any further
Investigating struct xdp_frame with pahole:
$ pahole -C xdp_frame net/core/xdp.o
struct xdp_frame {
void * data; /* 0 8 */
u16 len; /* 8 2 */
u16 headroom; /* 10 2 */
u32 metasize:8; /* 12: 0 4 */
u32 frame_sz:24; /* 12: 8 4 */
struct xdp_mem_info mem; /* 16 8 */
struct net_device * dev_rx; /* 24 8 */
/* size: 32, cachelines: 1, members: 7 */
/* last cacheline: 32 bytes */
};
pahole -C xdp_frame net/core/xdp.o
struct xdp_frame {
void * data; /* 0 8 */
u16 len; /* 8 2 */
u16 headroom; /* 10 2 */
u32 metasize:8; /* 12: 0 4 */
u32 frame_sz:24; /* 12: 8 4 */
struct xdp_mem_info mem; /* 16 8 */
struct net_device * dev_rx; /* 24 8 */
u16 flags; /* 32 2 */
/* size: 40, cachelines: 1, members: 8 */
/* padding: 6 */
/* last cacheline: 40 bytes */
};
$ pahole -C xdp_frame net/core/xdp.o
struct xdp_frame {
void * data; /* 0 8 */
u16 len; /* 8 2 */
u16 headroom; /* 10 2 */
u32 metasize:8; /* 12: 0 4 */
u32 frame_sz:24; /* 12: 8 4 */
struct xdp_mem_info mem; /* 16 8 */
struct net_device * dev_rx; /* 24 8 */
u32 flags; /* 32 4 */
/* size: 40, cachelines: 1, members: 8 */
/* padding: 4 */
/* last cacheline: 40 bytes */
};
Details for struct xdp_buff, it already contains 4 bytes padding.
$ pahole -C xdp_buff net/core/xdp.o
struct xdp_buff {
void * data; /* 0 8 */
void * data_end; /* 8 8 */
void * data_meta; /* 16 8 */
void * data_hard_start; /* 24 8 */
struct xdp_rxq_info * rxq; /* 32 8 */
struct xdp_txq_info * txq; /* 40 8 */
u32 frame_sz; /* 48 4 */
u16 flags; /* 52 2 */
/* size: 56, cachelines: 1, members: 8 */
/* padding: 2 */
/* last cacheline: 56 bytes */
};
