add the new memory allocator for netmap, which allocates memory

in small clusters instead of one big contiguous chunk.
This was already enabled in the previous commit.

1 files changed, 720 insertions, 0 deletions

diff --git a/sys/dev/netmap/netmap_mem2.c b/sys/dev/netmap/netmap_mem2.c
new file mode 100644
index 0000000..a307ec7
--- /dev/null
+++ b/sys/dev/netmap/netmap_mem2.c
@@ -0,0 +1,720 @@
+/*
+ * Copyright (C) 2012 Matteo Landi, Luigi Rizzo. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * $FreeBSD$
+ * $Id: netmap_mem2.c 10830 2012-03-22 18:06:01Z luigi $
+ *
+ * New memory allocator for netmap
+ */
+
+/*
+ * The new version allocates three regions:
+ *	nm_if_pool      for the struct netmap_if
+ *	nm_ring_pool    for the struct netmap_ring
+ *	nm_buf_pool    for the packet buffers.
+ *
+ * All regions need to be page-sized as we export them to
+ * userspace through mmap. Only the latter need to be dma-able,
+ * but for convenience use the same type of allocator for all.
+ *
+ * Once mapped, the three regions are exported to userspace
+ * as a contiguous block, starting from nm_if_pool. Each
+ * cluster (and pool) is an integral number of pages.
+ *   [ . . . ][ . . . . . .][ . . . . . . . . . .]
+ *    nm_if     nm_ring            nm_buf
+ *
+ * The userspace areas contain offsets of the objects in userspace.
+ * When (at init time) we write these offsets, we find out the index
+ * of the object, and from there locate the offset from the beginning
+ * of the region.
+ *
+ * Allocator for a pool of memory objects of the same size.
+ * The pool is split into smaller clusters, whose size is a
+ * multiple of the page size. The cluster size is chosen
+ * to minimize the waste for a given max cluster size
+ * (we do it by brute force, as we have relatively few object
+ * per cluster).
+ *
+ * To be polite with the cache, objects are aligned to
+ * the cache line, or 64 bytes. Sizes are rounded to multiple of 64.
+ * For each object we have
+ * one entry in the bitmap to signal the state. Allocation scans
+ * the bitmap, but since this is done only on attach, we are not
+ * too worried about performance
+ */
+
+/*
+ *	MEMORY SIZES:
+ *
+ * (all the parameters below will become tunables)
+ *
+ * struct netmap_if is variable size but small.
+ * Assuming each NIC has 8+2 rings, (4+1 tx, 4+1 rx) the netmap_if
+ * uses 120 bytes on a 64-bit machine.
+ * We allocate NETMAP_IF_MAX_SIZE  (1024) which should work even for
+ * cards with 48 ring pairs.
+ * The total number of 'struct netmap_if' could be slightly larger
+ * that the total number of rings on all interfaces on the system.
+ */
+#define NETMAP_IF_MAX_SIZE      1024
+#define NETMAP_IF_MAX_NUM       512
+
+/*
+ * netmap rings are up to 2..4k descriptors, 8 bytes each,
+ * plus some glue at the beginning (32 bytes).
+ * We set the default ring size to 9 pages (36K) and enable
+ * a few hundreds of them.
+ */
+#define NETMAP_RING_MAX_SIZE    (9*PAGE_SIZE)
+#define NETMAP_RING_MAX_NUM     200	/* approx 8MB */
+
+/*
+ * Buffers: the more the better. Buffer size is NETMAP_BUF_SIZE,
+ * 2k or slightly less, aligned to 64 bytes.
+ * A large 10G interface can have 2k*18 = 36k buffers per interface,
+ * or about 72MB of memory. Up to us to use more.
+ */
+#ifndef CONSERVATIVE
+#define NETMAP_BUF_MAX_NUM      100000  /* 200MB */
+#else /* CONSERVATIVE */
+#define NETMAP_BUF_MAX_NUM      20000   /* 40MB */
+#endif
+
+
+struct netmap_obj_pool {
+	char name[16];		/* name of the allocator */
+	u_int objtotal;         /* actual total number of objects. */
+	u_int objfree;          /* number of free objects. */
+	u_int clustentries;	/* actual objects per cluster */
+
+	/* the total memory space is _numclusters*_clustsize */
+	u_int _numclusters;	/* how many clusters */
+	u_int _clustsize;        /* cluster size */
+	u_int _objsize;		/* actual object size */
+
+	u_int _memtotal;	/* _numclusters*_clustsize */
+	struct lut_entry *lut;  /* virt,phys addresses, objtotal entries */
+	uint32_t *bitmap;       /* one bit per buffer, 1 means free */
+};
+
+struct netmap_mem_d {
+	NM_LOCK_T nm_mtx; /* protect the allocator ? */
+	u_int nm_totalsize; /* shorthand */
+
+	/* pointers to the three allocators */
+	struct netmap_obj_pool *nm_if_pool;
+	struct netmap_obj_pool *nm_ring_pool;
+	struct netmap_obj_pool *nm_buf_pool;
+};
+
+struct lut_entry *netmap_buffer_lut;	/* exported */
+
+
+/*
+ * Convert a userspace offset to a phisical address.
+ * XXX re-do in a simpler way.
+ *
+ * The idea here is to hide userspace applications the fact that pre-allocated
+ * memory is not contiguous, but fragmented across different clusters and
+ * smaller memory allocators. Consequently, first of all we need to find which
+ * allocator is owning provided offset, then we need to find out the physical
+ * address associated to target page (this is done using the look-up table.
+ */
+static inline vm_paddr_t
+netmap_ofstophys(vm_offset_t offset)
+{
+	const struct netmap_obj_pool *p[] = {
+		nm_mem->nm_if_pool,
+		nm_mem->nm_ring_pool,
+		nm_mem->nm_buf_pool };
+	int i;
+	vm_offset_t o = offset;
+
+
+	for (i = 0; i < 3; offset -= p[i]->_memtotal, i++) {
+		if (offset >= p[i]->_memtotal)
+			continue;
+		// XXX now scan the clusters
+		return p[i]->lut[offset / p[i]->_objsize].paddr +
+			offset % p[i]->_objsize;
+	}
+	D("invalid ofs 0x%x out of 0x%x 0x%x 0x%x", o,
+		p[0]->_memtotal, p[0]->_memtotal + p[1]->_memtotal,
+		p[0]->_memtotal + p[1]->_memtotal + p[2]->_memtotal);
+	return 0;	// XXX bad address
+}
+
+/*
+ * we store objects by kernel address, need to find the offset
+ * within the pool to export the value to userspace.
+ * Algorithm: scan until we find the cluster, then add the
+ * actual offset in the cluster
+ */
+ssize_t
+netmap_obj_offset(struct netmap_obj_pool *p, const void *vaddr)
+{
+	int i, k = p->clustentries, n = p->objtotal;
+	ssize_t ofs = 0;
+
+	for (i = 0; i < n; i += k, ofs += p->_clustsize) {
+		const char *base = p->lut[i].vaddr;
+		ssize_t relofs = (const char *) vaddr - base;
+
+		if (relofs < 0 || relofs > p->_clustsize)
+			continue;
+
+		ofs = ofs + relofs;
+		ND("%s: return offset %d (cluster %d) for pointer %p",
+		    p->name, ofs, i, vaddr);
+		return ofs;
+	}
+	D("address %p is not contained inside any cluster (%s)",
+	    vaddr, p->name);
+	return 0; /* An error occurred */
+}
+
+/* Helper functions which convert virtual addresses to offsets */
+#define netmap_if_offset(v)					\
+	netmap_obj_offset(nm_mem->nm_if_pool, (v))
+
+#define netmap_ring_offset(v)					\
+    (nm_mem->nm_if_pool->_memtotal + 				\
+	netmap_obj_offset(nm_mem->nm_ring_pool, (v)))
+
+#define netmap_buf_offset(v)					\
+    (nm_mem->nm_if_pool->_memtotal +				\
+	nm_mem->nm_ring_pool->_memtotal +			\
+	netmap_obj_offset(nm_mem->nm_buf_pool, (v)))
+
+
+static void *
+netmap_obj_malloc(struct netmap_obj_pool *p, int len)
+{
+	uint32_t i = 0;			/* index in the bitmap */
+	uint32_t mask, j;		/* slot counter */
+	void *vaddr = NULL;
+
+	if (len > p->_objsize) {
+		D("%s request size %d too large", p->name, len);
+		// XXX cannot reduce the size
+		return NULL;
+	}
+
+	if (p->objfree == 0) {
+		D("%s allocator: run out of memory", p->name);
+		return NULL;
+	}
+
+	/* termination is guaranteed by p->free */
+	while (vaddr == NULL) {
+		uint32_t cur = p->bitmap[i];
+		if (cur == 0) { /* bitmask is fully used */
+			i++;
+			continue;
+		}
+		/* locate a slot */
+		for (j = 0, mask = 1; (cur & mask) == 0; j++, mask <<= 1)
+			;
+
+		p->bitmap[i] &= ~mask; /* mark object as in use */
+		p->objfree--;
+
+		vaddr = p->lut[i * 32 + j].vaddr;
+	}
+	ND("%s allocator: allocated object @ [%d][%d]: vaddr %p", i, j, vaddr);
+
+	return vaddr;
+}
+
+
+/*
+ * free by index, not by address
+ */
+static void
+netmap_obj_free(struct netmap_obj_pool *p, uint32_t j)
+{
+	if (j >= p->objtotal) {
+		D("invalid index %u, max %u", j, p->objtotal);
+		return;
+	}
+	p->bitmap[j / 32] |= (1 << (j % 32));
+	p->objfree++;
+	return;
+}
+
+static void
+netmap_obj_free_va(struct netmap_obj_pool *p, void *vaddr)
+{
+	int i, j, n = p->_memtotal / p->_clustsize;
+
+	for (i = 0, j = 0; i < n; i++, j += p->clustentries) {
+		void *base = p->lut[i * p->clustentries].vaddr;
+		ssize_t relofs = (ssize_t) vaddr - (ssize_t) base;
+
+		/* Given address, is out of the scope of the current cluster.*/
+		if (vaddr < base || relofs > p->_clustsize)
+			continue;
+
+		j = j + relofs / p->_objsize;
+		KASSERT(j != 0, ("Cannot free object 0"));
+		netmap_obj_free(p, j);
+		return;
+	}
+	ND("address %p is not contained inside any cluster (%s)",
+	    vaddr, p->name);
+}
+
+#define netmap_if_malloc(len)	netmap_obj_malloc(nm_mem->nm_if_pool, len)
+#define netmap_if_free(v)	netmap_obj_free_va(nm_mem->nm_if_pool, (v))
+#define netmap_ring_malloc(len)	netmap_obj_malloc(nm_mem->nm_ring_pool, len)
+#define netmap_buf_malloc()			\
+	netmap_obj_malloc(nm_mem->nm_buf_pool, NETMAP_BUF_SIZE)
+
+
+/* Return the index associated to the given packet buffer */
+#define netmap_buf_index(v)						\
+    (netmap_obj_offset(nm_mem->nm_buf_pool, (v)) / nm_mem->nm_buf_pool->_objsize)
+
+
+static void
+netmap_new_bufs(struct netmap_if *nifp __unused,
+                struct netmap_slot *slot, u_int n)
+{
+	struct netmap_obj_pool *p = nm_mem->nm_buf_pool;
+	uint32_t i = 0;	/* slot counter */
+
+	for (i = 0; i < n; i++) {
+		void *vaddr = netmap_buf_malloc();
+		if (vaddr == NULL) {
+			D("unable to locate empty packet buffer");
+			goto cleanup;
+		}
+
+		slot[i].buf_idx = netmap_buf_index(vaddr);
+		KASSERT(slot[i].buf_idx != 0,
+		    ("Assigning buf_idx=0 to just created slot"));
+		slot[i].len = p->_objsize;
+		slot[i].flags = NS_BUF_CHANGED; // XXX GAETANO hack
+	}
+
+	ND("allocated %d buffers, %d available", n, p->objfree);
+	return;
+
+cleanup:
+	for (i--; i >= 0; i--) {
+		netmap_obj_free(nm_mem->nm_buf_pool, slot[i].buf_idx);
+	}
+}
+
+
+static void
+netmap_free_buf(struct netmap_if *nifp, uint32_t i)
+{
+	struct netmap_obj_pool *p = nm_mem->nm_buf_pool;
+	if (i < 2 || i >= p->objtotal) {
+		D("Cannot free buf#%d: should be in [2, %d[", i, p->objtotal);
+		return;
+	}
+	netmap_obj_free(nm_mem->nm_buf_pool, i);
+}
+
+
+/*
+ * Free all resources related to an allocator.
+ */
+static void
+netmap_destroy_obj_allocator(struct netmap_obj_pool *p)
+{
+	if (p == NULL)
+		return;
+	if (p->bitmap)
+		free(p->bitmap, M_NETMAP);
+	if (p->lut) {
+		int i;
+		for (i = 0; i < p->objtotal; i += p->clustentries) {
+			if (p->lut[i].vaddr)
+				contigfree(p->lut[i].vaddr, p->_clustsize, M_NETMAP);
+		}
+		bzero(p->lut, sizeof(struct lut_entry) * p->objtotal);
+		free(p->lut, M_NETMAP);
+	}
+	bzero(p, sizeof(*p));
+	free(p, M_NETMAP);
+}
+
+/*
+ * We receive a request for objtotal objects, of size objsize each.
+ * Internally we may round up both numbers, as we allocate objects
+ * in small clusters multiple of the page size.
+ * In the allocator we don't need to store the objsize,
+ * but we do need to keep track of objtotal' and clustentries,
+ * as they are needed when freeing memory.
+ *
+ * XXX note -- userspace needs the buffers to be contiguous,
+ *	so we cannot afford gaps at the end of a cluster.
+ */
+static struct netmap_obj_pool *
+netmap_new_obj_allocator(const char *name, u_int objtotal, u_int objsize)
+{
+	struct netmap_obj_pool *p;
+	int i, n;
+	u_int clustsize;	/* the cluster size, multiple of page size */
+	u_int clustentries;	/* how many objects per entry */
+
+#define MAX_CLUSTSIZE	(1<<17)
+#define LINE_ROUND	64
+	if (objsize >= MAX_CLUSTSIZE) {
+		/* we could do it but there is no point */
+		D("unsupported allocation for %d bytes", objsize);
+		return NULL;
+	}
+	/* make sure objsize is a multiple of LINE_ROUND */
+	i = (objsize & (LINE_ROUND - 1));
+	if (i) {
+		D("XXX aligning object by %d bytes", LINE_ROUND - i);
+		objsize += LINE_ROUND - i;
+	}
+	/*
+	 * Compute number of objects using a brute-force approach:
+	 * given a max cluster size,
+	 * we try to fill it with objects keeping track of the
+	 * wasted space to the next page boundary.
+	 */
+	for (clustentries = 0, i = 1;; i++) {
+		u_int delta, used = i * objsize;
+		if (used > MAX_CLUSTSIZE)
+			break;
+		delta = used % PAGE_SIZE;
+		if (delta == 0) { // exact solution
+			clustentries = i;
+			break;
+		}
+		if (delta > ( (clustentries*objsize) % PAGE_SIZE) )
+			clustentries = i;
+	}
+	// D("XXX --- ouch, delta %d (bad for buffers)", delta);
+	/* compute clustsize and round to the next page */
+	clustsize = clustentries * objsize;
+	i =  (clustsize & (PAGE_SIZE - 1));
+	if (i)
+		clustsize += PAGE_SIZE - i;
+	D("objsize %d clustsize %d objects %d",
+		objsize, clustsize, clustentries);
+
+	p = malloc(sizeof(struct netmap_obj_pool), M_NETMAP,
+	    M_WAITOK | M_ZERO);
+	if (p == NULL) {
+		D("Unable to create '%s' allocator", name);
+		return NULL;
+	}
+	/*
+	 * Allocate and initialize the lookup table.
+	 *
+	 * The number of clusters is n = ceil(objtotal/clustentries)
+	 * objtotal' = n * clustentries
+	 */
+	strncpy(p->name, name, sizeof(p->name));
+	p->clustentries = clustentries;
+	p->_clustsize = clustsize;
+	n = (objtotal + clustentries - 1) / clustentries;
+	p->_numclusters = n;
+	p->objtotal = n * clustentries;
+	p->objfree = p->objtotal - 2; /* obj 0 and 1 are reserved */
+	p->_objsize = objsize;
+	p->_memtotal = p->_numclusters * p->_clustsize;
+
+	p->lut = malloc(sizeof(struct lut_entry) * p->objtotal,
+	    M_NETMAP, M_WAITOK | M_ZERO);
+	if (p->lut == NULL) {
+		D("Unable to create lookup table for '%s' allocator", name);
+		goto clean;
+	}
+
+	/* Allocate the bitmap */
+	n = (p->objtotal + 31) / 32;
+	p->bitmap = malloc(sizeof(uint32_t) * n, M_NETMAP, M_WAITOK | M_ZERO);
+	if (p->bitmap == NULL) {
+		D("Unable to create bitmap (%d entries) for allocator '%s'", n,
+		    name);
+		goto clean;
+	}
+
+	/*
+	 * Allocate clusters, init pointers and bitmap
+	 */
+	for (i = 0; i < p->objtotal;) {
+		int lim = i + clustentries;
+		char *clust;
+
+		clust = contigmalloc(clustsize, M_NETMAP, M_WAITOK | M_ZERO,
+		    0, -1UL, PAGE_SIZE, 0);
+		if (clust == NULL) {
+			/*
+			 * If we get here, there is a severe memory shortage,
+			 * so halve the allocated memory to reclaim some.
+			 */
+			D("Unable to create cluster at %d for '%s' allocator",
+			    i, name);
+			lim = i / 2;
+			for (; i >= lim; i--) {
+				p->bitmap[ (i>>5) ] &=  ~( 1 << (i & 31) );
+				if (i % clustentries == 0 && p->lut[i].vaddr)
+					contigfree(p->lut[i].vaddr,
+						p->_clustsize, M_NETMAP);
+			}
+			p->objtotal = i;
+			p->objfree = p->objtotal - 2;
+			p->_numclusters = i / clustentries;
+			p->_memtotal = p->_numclusters * p->_clustsize;
+			break;
+		}
+		for (; i < lim; i++, clust += objsize) {
+			p->bitmap[ (i>>5) ] |=  ( 1 << (i & 31) );
+			p->lut[i].vaddr = clust;
+			p->lut[i].paddr = vtophys(clust);
+		}
+	}
+	p->bitmap[0] = ~3; /* objs 0 and 1 is always busy */
+	D("Pre-allocated %d clusters (%d/%dKB) for '%s'",
+	    p->_numclusters, p->_clustsize >> 10,
+	    p->_memtotal >> 10, name);
+
+	return p;
+
+clean:
+	netmap_destroy_obj_allocator(p);
+	return NULL;
+}
+
+static int
+netmap_memory_init(void)
+{
+	struct netmap_obj_pool *p;
+
+	nm_mem = malloc(sizeof(struct netmap_mem_d), M_NETMAP,
+			      M_WAITOK | M_ZERO);
+	if (nm_mem == NULL)
+		goto clean;
+
+	p = netmap_new_obj_allocator("netmap_if",
+	    NETMAP_IF_MAX_NUM, NETMAP_IF_MAX_SIZE);
+	if (p == NULL)
+		goto clean;
+	nm_mem->nm_if_pool = p;
+
+	p = netmap_new_obj_allocator("netmap_ring",
+	    NETMAP_RING_MAX_NUM, NETMAP_RING_MAX_SIZE);
+	if (p == NULL)
+		goto clean;
+	nm_mem->nm_ring_pool = p;
+
+	p = netmap_new_obj_allocator("netmap_buf",
+	    NETMAP_BUF_MAX_NUM, NETMAP_BUF_SIZE);
+	if (p == NULL)
+		goto clean;
+	netmap_total_buffers = p->objtotal;
+	netmap_buffer_lut = p->lut;
+	nm_mem->nm_buf_pool = p;
+	netmap_buffer_base = p->lut[0].vaddr;
+
+	mtx_init(&nm_mem->nm_mtx, "netmap memory allocator lock", NULL,
+		 MTX_DEF);
+	nm_mem->nm_totalsize =
+	    nm_mem->nm_if_pool->_memtotal +
+	    nm_mem->nm_ring_pool->_memtotal +
+	    nm_mem->nm_buf_pool->_memtotal;
+
+	D("Have %d KB for interfaces, %d KB for rings and %d MB for buffers",
+	    nm_mem->nm_if_pool->_memtotal >> 10,
+	    nm_mem->nm_ring_pool->_memtotal >> 10,
+	    nm_mem->nm_buf_pool->_memtotal >> 20);
+	return 0;
+
+clean:
+	if (nm_mem) {
+		netmap_destroy_obj_allocator(nm_mem->nm_ring_pool);
+		netmap_destroy_obj_allocator(nm_mem->nm_if_pool);
+		free(nm_mem, M_NETMAP);
+	}
+	return ENOMEM;
+}
+
+
+static void
+netmap_memory_fini(void)
+{
+	if (!nm_mem)
+		return;
+	netmap_destroy_obj_allocator(nm_mem->nm_if_pool);
+	netmap_destroy_obj_allocator(nm_mem->nm_ring_pool);
+	netmap_destroy_obj_allocator(nm_mem->nm_buf_pool);
+	mtx_destroy(&nm_mem->nm_mtx);
+	free(nm_mem, M_NETMAP);
+}
+
+
+
+static void *
+netmap_if_new(const char *ifname, struct netmap_adapter *na)
+{
+	struct netmap_if *nifp;
+	struct netmap_ring *ring;
+	ssize_t base; /* handy for relative offsets between rings and nifp */
+	u_int i, len, ndesc;
+	u_int ntx = na->num_tx_rings + 1; /* shorthand, include stack ring */
+	u_int nrx = na->num_rx_rings + 1; /* shorthand, include stack ring */
+	struct netmap_kring *kring;
+
+	NMA_LOCK();
+	/*
+	 * the descriptor is followed inline by an array of offsets
+	 * to the tx and rx rings in the shared memory region.
+	 */
+	len = sizeof(struct netmap_if) + (nrx + ntx) * sizeof(ssize_t);
+	nifp = netmap_if_malloc(len);
+	if (nifp == NULL) {
+		NMA_UNLOCK();
+		return NULL;
+	}
+
+	/* initialize base fields -- override const */
+	*(int *)(uintptr_t)&nifp->ni_tx_rings = na->num_tx_rings;
+	*(int *)(uintptr_t)&nifp->ni_rx_rings = na->num_rx_rings;
+	strncpy(nifp->ni_name, ifname, IFNAMSIZ);
+
+	(na->refcount)++;	/* XXX atomic ? we are under lock */
+	if (na->refcount > 1) { /* already setup, we are done */
+		NMA_UNLOCK();
+		goto final;
+	}
+
+	/*
+	 * First instance, allocate netmap rings and buffers for this card
+	 * The rings are contiguous, but have variable size.
+	 */
+	for (i = 0; i < ntx; i++) { /* Transmit rings */
+		kring = &na->tx_rings[i];
+		ndesc = na->num_tx_desc;
+		bzero(kring, sizeof(*kring));
+		len = sizeof(struct netmap_ring) +
+			  ndesc * sizeof(struct netmap_slot);
+		ring = netmap_ring_malloc(len);
+		if (ring == NULL) {
+			D("Cannot allocate tx_ring[%d] for %s", i, ifname);
+			goto cleanup;
+		}
+		ND("txring[%d] at %p ofs %d", i, ring);
+		kring->na = na;
+		kring->ring = ring;
+		*(int *)(uintptr_t)&ring->num_slots = kring->nkr_num_slots = ndesc;
+		*(ssize_t *)(uintptr_t)&ring->buf_ofs =
+		    (nm_mem->nm_if_pool->_memtotal +
+			nm_mem->nm_ring_pool->_memtotal) -
+			netmap_ring_offset(ring);
+
+		/*
+		 * IMPORTANT:
+		 * Always keep one slot empty, so we can detect new
+		 * transmissions comparing cur and nr_hwcur (they are
+		 * the same only if there are no new transmissions).
+		 */
+		ring->avail = kring->nr_hwavail = ndesc - 1;
+		ring->cur = kring->nr_hwcur = 0;
+		*(int *)(uintptr_t)&ring->nr_buf_size = NETMAP_BUF_SIZE;
+		ND("initializing slots for txring[%d]", i);
+		netmap_new_bufs(nifp, ring->slot, ndesc);
+	}
+
+	for (i = 0; i < nrx; i++) { /* Receive rings */
+		kring = &na->rx_rings[i];
+		ndesc = na->num_rx_desc;
+		bzero(kring, sizeof(*kring));
+		len = sizeof(struct netmap_ring) +
+			  ndesc * sizeof(struct netmap_slot);
+		ring = netmap_ring_malloc(len);
+		if (ring == NULL) {
+			D("Cannot allocate rx_ring[%d] for %s", i, ifname);
+			goto cleanup;
+		}
+		ND("rxring[%d] at %p ofs %d", i, ring);
+
+		kring->na = na;
+		kring->ring = ring;
+		*(int *)(uintptr_t)&ring->num_slots = kring->nkr_num_slots = ndesc;
+		*(ssize_t *)(uintptr_t)&ring->buf_ofs =
+		    (nm_mem->nm_if_pool->_memtotal +
+		        nm_mem->nm_ring_pool->_memtotal) -
+			netmap_ring_offset(ring);
+
+		ring->cur = kring->nr_hwcur = 0;
+		ring->avail = kring->nr_hwavail = 0; /* empty */
+		*(int *)(uintptr_t)&ring->nr_buf_size = NETMAP_BUF_SIZE;
+		ND("initializing slots for rxring[%d]", i);
+		netmap_new_bufs(nifp, ring->slot, ndesc);
+	}
+	NMA_UNLOCK();
+#ifdef linux
+	// XXX initialize the selrecord structs.
+	for (i = 0; i < ntx; i++)
+		init_waitqueue_head(&na->rx_rings[i].si);
+	for (i = 0; i < nrx; i++)
+		init_waitqueue_head(&na->tx_rings[i].si);
+	init_waitqueue_head(&na->rx_si);
+	init_waitqueue_head(&na->tx_si);
+#endif
+final:
+	/*
+	 * fill the slots for the rx and tx rings. They contain the offset
+	 * between the ring and nifp, so the information is usable in
+	 * userspace to reach the ring from the nifp.
+	 */
+	base = netmap_if_offset(nifp);
+	for (i = 0; i < ntx; i++) {
+		*(ssize_t *)(uintptr_t)&nifp->ring_ofs[i] =
+			netmap_ring_offset(na->tx_rings[i].ring) - base;
+	}
+	for (i = 0; i < nrx; i++) {
+		*(ssize_t *)(uintptr_t)&nifp->ring_ofs[i+ntx] =
+			netmap_ring_offset(na->rx_rings[i].ring) - base;
+	}
+	return (nifp);
+cleanup:
+	// XXX missing
+	NMA_UNLOCK();
+	return NULL;
+}
+
+static void
+netmap_free_rings(struct netmap_adapter *na)
+{
+	int i;
+	for (i = 0; i < na->num_tx_rings + 1; i++)
+		netmap_obj_free_va(nm_mem->nm_ring_pool,
+			na->tx_rings[i].ring);
+	for (i = 0; i < na->num_rx_rings + 1; i++)
+		netmap_obj_free_va(nm_mem->nm_ring_pool,
+			na->rx_rings[i].ring);
+}