Hi:
[NET] back: Add TSO support
This patch adds TCP Segmentation Offload (TSO) support to the backend.
It also advertises this fact through xenbus so that the frontend can
detect this and send through TSO requests only if it is supported.
This is done using an extra request slot which is indicated by a flag
in the first slot. In future checksum offload can be done in the same
way.
The extra request slot must not be generated if the backend does not
support the appropriate feature bits. For now this is simply feature-tso.
If the frontend detects the presence of the appropriate feature bits,
it may generate TX requests which have the appropriate request flags
set that indicates the presence of an extra request slot with the extra
information.
On the backend the extra request slot is read if and only if the request
flags are set in the TX request.
This protocol allows more feature bits to be added in future without
breaking compatibility. At least the hardware checksum bit is planned.
Even though only TSO is supported for now the code actually supports
GSO so it can be applied to any other protocol. The only missing bit
is the detection of host support for a specific GSO protocol. Once that
is added we can advertise all supported protocols to the guest.
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
diff -r 7ec216a8bc14 -r 9853b45712e8
linux-2.6-xen-sparse/drivers/xen/netback/netback.c
--- a/linux-2.6-xen-sparse/drivers/xen/netback/netback.c Wed Jun 28
13:51:21 2006 +1000
+++ b/linux-2.6-xen-sparse/drivers/xen/netback/netback.c Wed Jun 28
13:55:13 2006 +1000
@@ -490,14 +490,16 @@ inline static void net_tx_action_dealloc
}
}
-static void netbk_tx_err(netif_t *netif, RING_IDX end)
+static void netbk_tx_err(netif_t *netif, netif_tx_request_t *txp, RING_IDX end)
{
RING_IDX cons = netif->tx.req_cons;
do {
- netif_tx_request_t *txp = RING_GET_REQUEST(&netif->tx, cons);
make_tx_response(netif, txp, NETIF_RSP_ERROR);
- } while (++cons < end);
+ if (++cons >= end)
+ break;
+ txp = RING_GET_REQUEST(&netif->tx, cons);
+ } while (1);
netif->tx.req_cons = cons;
netif_schedule_work(netif);
netif_put(netif);
@@ -508,7 +510,7 @@ static int netbk_count_requests(netif_t
{
netif_tx_request_t *first = txp;
RING_IDX cons = netif->tx.req_cons;
- int frags = 1;
+ int frags = 0;
while (txp->flags & NETTXF_more_data) {
if (frags >= work_to_do) {
@@ -543,7 +545,7 @@ static gnttab_map_grant_ref_t *netbk_get
skb_frag_t *frags = shinfo->frags;
netif_tx_request_t *txp;
unsigned long pending_idx = *((u16 *)skb->data);
- RING_IDX cons = netif->tx.req_cons + 1;
+ RING_IDX cons = netif->tx.req_cons;
int i, start;
/* Skip first skb fragment if it is on same page as header fragment. */
@@ -668,6 +670,7 @@ static void net_tx_action(unsigned long
struct sk_buff *skb;
netif_t *netif;
netif_tx_request_t txreq;
+ struct netif_tx_extra txtra;
u16 pending_idx;
RING_IDX i;
gnttab_map_grant_ref_t *mop;
@@ -726,22 +729,37 @@ static void net_tx_action(unsigned long
}
netif->remaining_credit -= txreq.size;
+ work_to_do--;
+ netif->tx.req_cons = ++i;
+
+ if (txreq.flags & NETTXF_extra_info) {
+ if (work_to_do-- <= 0) {
+ DPRINTK("Missing extra info\n");
+ netbk_tx_err(netif, &txreq, i);
+ continue;
+ }
+
+ memcpy(&txtra, RING_GET_REQUEST(&netif->tx, i),
+ sizeof(txtra));
+ netif->tx.req_cons = ++i;
+ }
+
ret = netbk_count_requests(netif, &txreq, work_to_do);
if (unlikely(ret < 0)) {
- netbk_tx_err(netif, i - ret);
+ netbk_tx_err(netif, &txreq, i - ret);
continue;
}
i += ret;
if (unlikely(ret > MAX_SKB_FRAGS + 1)) {
DPRINTK("Too many frags\n");
- netbk_tx_err(netif, i);
+ netbk_tx_err(netif, &txreq, i);
continue;
}
if (unlikely(txreq.size < ETH_HLEN)) {
DPRINTK("Bad packet size: %d\n", txreq.size);
- netbk_tx_err(netif, i);
+ netbk_tx_err(netif, &txreq, i);
continue;
}
@@ -750,25 +768,31 @@ static void net_tx_action(unsigned long
DPRINTK("txreq.offset: %x, size: %u, end: %lu\n",
txreq.offset, txreq.size,
(txreq.offset &~PAGE_MASK) + txreq.size);
- netbk_tx_err(netif, i);
+ netbk_tx_err(netif, &txreq, i);
continue;
}
pending_idx = pending_ring[MASK_PEND_IDX(pending_cons)];
data_len = (txreq.size > PKT_PROT_LEN &&
- ret < MAX_SKB_FRAGS + 1) ?
+ ret < MAX_SKB_FRAGS) ?
PKT_PROT_LEN : txreq.size;
skb = alloc_skb(data_len+16, GFP_ATOMIC);
if (unlikely(skb == NULL)) {
DPRINTK("Can't allocate a skb in start_xmit.\n");
- netbk_tx_err(netif, i);
+ netbk_tx_err(netif, &txreq, i);
break;
}
/* Packets passed to netif_rx() must have some headroom. */
skb_reserve(skb, 16);
+
+ if (txreq.flags & NETTXF_gso) {
+ skb_shinfo(skb)->gso_size = txtra.gso_size;
+ skb_shinfo(skb)->gso_segs = txtra.gso_segs;
+ skb_shinfo(skb)->gso_type = txtra.gso_type;
+ }
gnttab_set_map_op(mop, MMAP_VADDR(pending_idx),
GNTMAP_host_map | GNTMAP_readonly,
@@ -782,7 +806,7 @@ static void net_tx_action(unsigned long
__skb_put(skb, data_len);
- skb_shinfo(skb)->nr_frags = ret - 1;
+ skb_shinfo(skb)->nr_frags = ret;
if (data_len < txreq.size) {
skb_shinfo(skb)->nr_frags++;
skb_shinfo(skb)->frags[0].page =
@@ -908,6 +932,9 @@ static void make_tx_response(netif_t *ne
resp = RING_GET_RESPONSE(&netif->tx, i);
resp->id = txp->id;
resp->status = st;
+
+ if (txp->flags & NETTXF_extra_info)
+ RING_GET_RESPONSE(&netif->tx, ++i)->status = NETIF_RSP_NULL;
netif->tx.rsp_prod_pvt = ++i;
RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&netif->tx, notify);
diff -r 7ec216a8bc14 -r 9853b45712e8
linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c
--- a/linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c Wed Jun 28 13:51:21
2006 +1000
+++ b/linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c Wed Jun 28 13:55:13
2006 +1000
@@ -101,6 +101,12 @@ static int netback_probe(struct xenbus_d
goto abort_transaction;
}
+ err = xenbus_printf(xbt, dev->nodename, "feature-tso", "%d", 1);
+ if (err) {
+ message = "writing feature-tso";
+ goto abort_transaction;
+ }
+
err = xenbus_transaction_end(xbt, 0);
} while (err == -EAGAIN);
diff -r 7ec216a8bc14 -r 9853b45712e8 xen/include/public/io/netif.h
--- a/xen/include/public/io/netif.h Wed Jun 28 13:51:21 2006 +1000
+++ b/xen/include/public/io/netif.h Wed Jun 28 13:55:13 2006 +1000
@@ -31,6 +31,13 @@
#define _NETTXF_more_data (2)
#define NETTXF_more_data (1U<<_NETTXF_more_data)
+/* Packet has GSO fields. */
+#define _NETTXF_gso (3)
+#define NETTXF_gso (1U<<_NETTXF_gso)
+
+/* Packet to be folloed by extra descritptor. */
+#define NETTXF_extra_info (NETTXF_gso)
+
struct netif_tx_request {
grant_ref_t gref; /* Reference to buffer page */
uint16_t offset; /* Offset within buffer page */
@@ -39,6 +46,13 @@ struct netif_tx_request {
uint16_t size; /* Packet size in bytes. */
};
typedef struct netif_tx_request netif_tx_request_t;
+
+/* This structure needs to fit within netif_tx_request for compatibility. */
+struct netif_tx_extra {
+ uint16_t gso_size; /* GSO MSS. */
+ uint16_t gso_segs; /* GSO segment count. */
+ uint16_t gso_type; /* GSO type. */
+};
struct netif_tx_response {
uint16_t id;
@@ -78,6 +92,7 @@ DEFINE_RING_TYPES(netif_rx, struct netif
#define NETIF_RSP_DROPPED -2
#define NETIF_RSP_ERROR -1
#define NETIF_RSP_OKAY 0
+#define NETIF_RSP_NULL 1
#endif
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