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Subject[PATCH 3/3] Let host NIC driver to DMA to guest user space.
Date
The patch let host NIC driver to receive user space skb,
then the driver has chance to directly DMA to guest user
space buffers thru single ethX interface.

Signed-off-by: Xin Xiaohui <xiaohui.xin@intel.com>
Signed-off-by: Zhao Yu <yzhao81@gmail.com>
Sigend-off-by: Jeff Dike <jdike@c2.user-mode-linux.org>
---
include/linux/netdevice.h | 72 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/skbuff.h | 32 ++++++++++++++++++--
net/core/dev.c | 27 +++++++++++++++++
net/core/skbuff.c | 62 +++++++++++++++++++++++++++++++++++----
4 files changed, 184 insertions(+), 9 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 94958c1..0de8688 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -486,6 +486,16 @@ struct netdev_queue {
} ____cacheline_aligned_in_smp;


+struct netdev_page_ctor {
+ int hdr_len;
+ int data_len;
+ int npages;
+ unsigned flags;
+ struct socket *sock;
+ struct skb_user_page *(*ctor)(struct netdev_page_ctor *,
+ struct sk_buff *, int);
+};
+
/*
* This structure defines the management hooks for network devices.
* The following hooks can be defined; unless noted otherwise, they are
@@ -636,6 +646,8 @@ struct net_device_ops {
int (*ndo_fcoe_ddp_done)(struct net_device *dev,
u16 xid);
#endif
+ int (*ndo_page_ctor_prep)(struct net_device *dev,
+ struct netdev_page_ctor *ctor);
};

/*
@@ -916,6 +928,7 @@ struct net_device
/* max exchange id for FCoE LRO by ddp */
unsigned int fcoe_ddp_xid;
#endif
+ struct netdev_page_ctor *page_ctor;
};
#define to_net_dev(d) container_of(d, struct net_device, dev)

@@ -2013,6 +2026,65 @@ static inline u32 dev_ethtool_get_flags(struct net_device *dev)
return 0;
return dev->ethtool_ops->get_flags(dev);
}
+
+static inline int netdev_page_ctor_prep(struct net_device *dev,
+ struct netdev_page_ctor *ctor)
+{
+ int rc;
+ int npages, data_len;
+ const struct net_device_ops *ops = dev->netdev_ops;
+
+ /* needed by packet split */
+ if (ops->ndo_page_ctor_prep) {
+ rc = ops->ndo_page_ctor_prep(dev, ctor);
+ if (rc)
+ return rc;
+ } else { /* should be temp */
+ ctor->hdr_len = 128;
+ ctor->data_len = 2048;
+ ctor->npages = 1;
+ }
+
+ if (ctor->hdr_len <= 0)
+ goto err;
+
+ npages = ctor->npages;
+ data_len = ctor->data_len;
+ if (npages <= 0 || npages > MAX_SKB_FRAGS ||
+ (data_len < PAGE_SIZE * (npages - 1) ||
+ data_len > PAGE_SIZE * npages))
+ goto err;
+
+ return 0;
+err:
+ dev_warn(&dev->dev, "invalid page constructor parameters\n");
+
+ return -EINVAL;
+}
+
+static inline int netdev_page_ctor_attach(struct net_device *dev,
+ struct netdev_page_ctor *ctor)
+{
+ if (dev->flags & IFF_UP)
+ return -EBUSY;
+
+ if (rcu_dereference(dev->page_ctor))
+ return -EBUSY;
+
+ rcu_assign_pointer(dev->page_ctor, ctor);
+
+ return 0;
+}
+
+static inline void netdev_page_ctor_detach(struct net_device *dev)
+{
+ if (!rcu_dereference(dev->page_ctor))
+ return;
+
+ rcu_assign_pointer(dev->page_ctor, NULL);
+ synchronize_rcu();
+}
+
#endif /* __KERNEL__ */

#endif /* _LINUX_NETDEVICE_H */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index df7b23a..c77837e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -209,6 +209,13 @@ struct skb_shared_info {
void * destructor_arg;
};

+struct skb_user_page {
+ u8 *start;
+ int size;
+ struct skb_frag_struct *frags;
+ struct skb_shared_info *ushinfo;
+ void (*dtor)(struct skb_user_page *);
+};
/* We divide dataref into two halves. The higher 16 bits hold references
* to the payload part of skb->data. The lower 16 bits hold references to
* the entire skb->data. A clone of a headerless skb holds the length of
@@ -441,17 +448,18 @@ extern void kfree_skb(struct sk_buff *skb);
extern void consume_skb(struct sk_buff *skb);
extern void __kfree_skb(struct sk_buff *skb);
extern struct sk_buff *__alloc_skb(unsigned int size,
- gfp_t priority, int fclone, int node);
+ gfp_t priority, int fclone,
+ int node, struct net_device *dev);
static inline struct sk_buff *alloc_skb(unsigned int size,
gfp_t priority)
{
- return __alloc_skb(size, priority, 0, -1);
+ return __alloc_skb(size, priority, 0, -1, NULL);
}

static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
gfp_t priority)
{
- return __alloc_skb(size, priority, 1, -1);
+ return __alloc_skb(size, priority, 1, -1, NULL);
}

extern int skb_recycle_check(struct sk_buff *skb, int skb_size);
@@ -1509,6 +1517,24 @@ static inline void netdev_free_page(struct net_device *dev, struct page *page)
__free_page(page);
}

+extern struct skb_user_page *netdev_alloc_user_pages(struct net_device *dev,
+ struct sk_buff *skb, int npages);
+
+extern int netdev_use_ps_feature(struct net_device *dev);
+
+static inline struct skb_user_page *netdev_alloc_user_page(
+ struct net_device *dev,
+ struct sk_buff *skb, unsigned int size)
+{
+ struct skb_user_page *user;
+ int npages = (size < PAGE_SIZE) ? 1 : (size / PAGE_SIZE);
+
+ user = netdev_alloc_user_pages(dev, skb, npages);
+ if (likely(user))
+ return user;
+ return NULL;
+}
+
/**
* skb_clone_writable - is the header of a clone writable
* @skb: buffer to check
diff --git a/net/core/dev.c b/net/core/dev.c
index b8f74cf..9d2c2ba 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2265,6 +2265,27 @@ void netif_nit_deliver(struct sk_buff *skb)
rcu_read_unlock();
}

+static inline struct sk_buff *handle_user_space_buf(struct sk_buff *skb,
+ struct packet_type **pt_prev,
+ int *ret, struct net_device *orig_dev)
+{
+ struct netdev_page_ctor *ctor = NULL;
+ struct sock *sk = NULL;
+
+ if (skb->dev)
+ ctor = skb->dev->page_ctor;
+ if (!ctor)
+ return skb;
+
+ sk = ctor->sock->sk;
+
+ skb_queue_tail(&sk->sk_receive_queue, skb);
+
+ sk->sk_data_ready(sk, skb->len);
+ return NULL;
+}
+
+
/**
* netif_receive_skb - process receive buffer from network
* @skb: buffer to process
@@ -2342,6 +2363,9 @@ int netif_receive_skb(struct sk_buff *skb)
goto out;
ncls:
#endif
+ skb = handle_user_space_buf(skb, &pt_prev, &ret, orig_dev);
+ if (!skb)
+ goto out;

skb = handle_bridge(skb, &pt_prev, &ret, orig_dev);
if (!skb)
@@ -2455,6 +2479,9 @@ int dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
if (skb_is_gso(skb) || skb_has_frags(skb))
goto normal;

+ if (skb->dev && skb->dev->page_ctor)
+ goto normal;
+
rcu_read_lock();
list_for_each_entry_rcu(ptype, head, list) {
if (ptype->type != type || ptype->dev || !ptype->gro_receive)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 80a9616..40461d5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -170,12 +170,13 @@ EXPORT_SYMBOL(skb_under_panic);
* %GFP_ATOMIC.
*/
struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
- int fclone, int node)
+ int fclone, int node, struct net_device *dev)
{
struct kmem_cache *cache;
struct skb_shared_info *shinfo;
struct sk_buff *skb;
u8 *data;
+ struct skb_user_page *user = NULL;

cache = fclone ? skbuff_fclone_cache : skbuff_head_cache;

@@ -185,8 +186,22 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
goto out;

size = SKB_DATA_ALIGN(size);
- data = kmalloc_node_track_caller(size + sizeof(struct skb_shared_info),
- gfp_mask, node);
+
+ if (!dev || !dev->page_ctor) { /* Legacy alloc func */
+ data = kmalloc_node_track_caller(
+ size + sizeof(struct skb_shared_info),
+ gfp_mask, node);
+ } else { /* Allocation may from page constructor of device */
+ user = netdev_alloc_user_page(dev, skb, size);
+ if (!user)
+ data = kmalloc_node_track_caller(
+ size + sizeof(struct skb_shared_info),
+ gfp_mask, node);
+ else {
+ data = user->start;
+ size = SKB_DATA_ALIGN(user->size);
+ }
+ }
if (!data)
goto nodata;

@@ -208,6 +223,10 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
skb->mac_header = ~0U;
#endif

+ if (user)
+ memcpy(user->ushinfo, skb_shinfo(skb),
+ sizeof(struct skb_shared_info));
+
/* make sure we initialize shinfo sequentially */
shinfo = skb_shinfo(skb);
atomic_set(&shinfo->dataref, 1);
@@ -231,6 +250,9 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,

child->fclone = SKB_FCLONE_UNAVAILABLE;
}
+
+ shinfo->destructor_arg = user;
+
out:
return skb;
nodata:
@@ -259,7 +281,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
int node = dev->dev.parent ? dev_to_node(dev->dev.parent) : -1;
struct sk_buff *skb;

- skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, node);
+ skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, node, dev);
if (likely(skb)) {
skb_reserve(skb, NET_SKB_PAD);
skb->dev = dev;
@@ -278,6 +300,27 @@ struct page *__netdev_alloc_page(struct net_device *dev, gfp_t gfp_mask)
}
EXPORT_SYMBOL(__netdev_alloc_page);

+struct skb_user_page *netdev_alloc_user_pages(struct net_device *dev,
+ struct sk_buff *skb, int npages)
+{
+ struct netdev_page_ctor *ctor;
+ struct skb_user_page *user = NULL;
+
+ rcu_read_lock();
+ ctor = rcu_dereference(dev->page_ctor);
+ if (!ctor)
+ goto out;
+
+ BUG_ON(npages > ctor->npages);
+
+ user = ctor->ctor(ctor, skb, npages);
+out:
+ rcu_read_unlock();
+
+ return user;
+}
+EXPORT_SYMBOL(netdev_alloc_user_pages);
+
void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
int size)
{
@@ -338,6 +381,8 @@ static void skb_clone_fraglist(struct sk_buff *skb)

static void skb_release_data(struct sk_buff *skb)
{
+ struct skb_user_page *user = skb_shinfo(skb)->destructor_arg;
+
if (!skb->cloned ||
!atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
&skb_shinfo(skb)->dataref)) {
@@ -349,7 +394,8 @@ static void skb_release_data(struct sk_buff *skb)

if (skb_has_frags(skb))
skb_drop_fraglist(skb);
-
+ if (skb->dev && skb->dev->page_ctor && user && user->dtor)
+ user->dtor(user);
kfree(skb->head);
}
}
@@ -503,8 +549,12 @@ int skb_recycle_check(struct sk_buff *skb, int skb_size)
if (skb_shared(skb) || skb_cloned(skb))
return 0;

- skb_release_head_state(skb);
+ if (skb->dev && skb->dev->page_ctor)
+ return 0;
+
shinfo = skb_shinfo(skb);
+
+ skb_release_head_state(skb);
atomic_set(&shinfo->dataref, 1);
shinfo->nr_frags = 0;
shinfo->gso_size = 0;
--
1.5.4.4


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