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    Subject[PATCH 4/9] [I/OAT] Utility functions for offloading sk_buff to iovec copies
    Date
    Provides for pinning user space pages in memory, copying to iovecs,
    and copying from sk_buffs including fragmented and chained sk_buffs.

    Signed-off-by: Chris Leech <christopher.leech@intel.com>
    ---
    drivers/dma/Makefile | 3
    drivers/dma/iovlock.c | 301 +++++++++++++++++++++++++++++++++++++++++++++
    include/linux/dmaengine.h | 22 +++
    include/net/netdma.h | 6 +
    net/core/Makefile | 1
    net/core/user_dma.c | 127 +++++++++++++++++++
    6 files changed, 459 insertions(+), 1 deletions(-)
    diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
    index c8a5f56..bdcfdbd 100644
    --- a/drivers/dma/Makefile
    +++ b/drivers/dma/Makefile
    @@ -1,2 +1,3 @@
    -obj-y += dmaengine.o
    +obj-$(CONFIG_DMA_ENGINE) += dmaengine.o
    +obj-$(CONFIG_NET_DMA) += iovlock.o
    obj-$(CONFIG_INTEL_IOATDMA) += ioatdma.o
    diff --git a/drivers/dma/iovlock.c b/drivers/dma/iovlock.c
    new file mode 100644
    index 0000000..5ed327e
    --- /dev/null
    +++ b/drivers/dma/iovlock.c
    @@ -0,0 +1,301 @@
    +/*
    + * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
    + * Portions based on net/core/datagram.c and copyrighted by their authors.
    + *
    + * This program is free software; you can redistribute it and/or modify it
    + * under the terms of the GNU General Public License as published by the Free
    + * Software Foundation; either version 2 of the License, or (at your option)
    + * any later version.
    + *
    + * This program is distributed in the hope that it will be useful, but WITHOUT
    + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
    + * more details.
    + *
    + * You should have received a copy of the GNU General Public License along with
    + * this program; if not, write to the Free Software Foundation, Inc., 59
    + * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
    + *
    + * The full GNU General Public License is included in this distribution in the
    + * file called COPYING.
    + */
    +
    +/*
    + * This code allows the net stack to make use of a DMA engine for
    + * skb to iovec copies.
    + */
    +
    +#include <linux/dmaengine.h>
    +#include <linux/pagemap.h>
    +#include <net/tcp.h> /* for memcpy_toiovec */
    +#include <asm/io.h>
    +#include <asm/uaccess.h>
    +
    +int num_pages_spanned(struct iovec *iov)
    +{
    + return
    + ((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
    + ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
    +}
    +
    +/*
    + * Pin down all the iovec pages needed for len bytes.
    + * Return a struct dma_pinned_list to keep track of pages pinned down.
    + *
    + * We are allocating a single chunk of memory, and then carving it up into
    + * 3 sections, the latter 2 whose size depends on the number of iovecs and the
    + * total number of pages, respectively.
    + */
    +struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
    +{
    + struct dma_pinned_list *local_list;
    + struct page **pages;
    + int i;
    + int ret;
    + int nr_iovecs = 0;
    + int iovec_len_used = 0;
    + int iovec_pages_used = 0;
    + long err;
    +
    + /* don't pin down non-user-based iovecs */
    + if (segment_eq(get_fs(), KERNEL_DS))
    + return NULL;
    +
    + /* determine how many iovecs/pages there are, up front */
    + do {
    + iovec_len_used += iov[nr_iovecs].iov_len;
    + iovec_pages_used += num_pages_spanned(&iov[nr_iovecs]);
    + nr_iovecs++;
    + } while (iovec_len_used < len);
    +
    + /* single kmalloc for pinned list, page_list[], and the page arrays */
    + local_list = kmalloc(sizeof(*local_list)
    + + (nr_iovecs * sizeof (struct dma_page_list))
    + + (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
    + if (!local_list) {
    + err = -ENOMEM;
    + goto out;
    + }
    +
    + /* list of pages starts right after the page list array */
    + pages = (struct page **) &local_list->page_list[nr_iovecs];
    +
    + for (i = 0; i < nr_iovecs; i++) {
    + struct dma_page_list *page_list = &local_list->page_list[i];
    +
    + len -= iov[i].iov_len;
    +
    + if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len)) {
    + err = -EFAULT;
    + goto unpin;
    + }
    +
    + page_list->nr_pages = num_pages_spanned(&iov[i]);
    + page_list->base_address = iov[i].iov_base;
    +
    + page_list->pages = pages;
    + pages += page_list->nr_pages;
    +
    + /* pin pages down */
    + down_read(&current->mm->mmap_sem);
    + ret = get_user_pages(
    + current,
    + current->mm,
    + (unsigned long) iov[i].iov_base,
    + page_list->nr_pages,
    + 1, /* write */
    + 0, /* force */
    + page_list->pages,
    + NULL);
    + up_read(&current->mm->mmap_sem);
    +
    + if (ret != page_list->nr_pages) {
    + err = -ENOMEM;
    + goto unpin;
    + }
    +
    + local_list->nr_iovecs = i + 1;
    + }
    +
    + return local_list;
    +
    +unpin:
    + dma_unpin_iovec_pages(local_list);
    +out:
    + return ERR_PTR(err);
    +}
    +
    +void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
    +{
    + int i, j;
    +
    + if (!pinned_list)
    + return;
    +
    + for (i = 0; i < pinned_list->nr_iovecs; i++) {
    + struct dma_page_list *page_list = &pinned_list->page_list[i];
    + for (j = 0; j < page_list->nr_pages; j++) {
    + set_page_dirty_lock(page_list->pages[j]);
    + page_cache_release(page_list->pages[j]);
    + }
    + }
    +
    + kfree(pinned_list);
    +}
    +
    +static dma_cookie_t dma_memcpy_to_kernel_iovec(struct dma_chan *chan, struct
    + iovec *iov, unsigned char *kdata, size_t len)
    +{
    + dma_cookie_t dma_cookie = 0;
    +
    + while (len > 0) {
    + if (iov->iov_len) {
    + int copy = min_t(unsigned int, iov->iov_len, len);
    + dma_cookie = dma_async_memcpy_buf_to_buf(
    + chan,
    + iov->iov_base,
    + kdata,
    + copy);
    + kdata += copy;
    + len -= copy;
    + iov->iov_len -= copy;
    + iov->iov_base += copy;
    + }
    + iov++;
    + }
    +
    + return dma_cookie;
    +}
    +
    +/*
    + * We have already pinned down the pages we will be using in the iovecs.
    + * Each entry in iov array has corresponding entry in pinned_list->page_list.
    + * Using array indexing to keep iov[] and page_list[] in sync.
    + * Initial elements in iov array's iov->iov_len will be 0 if already copied into
    + * by another call.
    + * iov array length remaining guaranteed to be bigger than len.
    + */
    +dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
    + struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len)
    +{
    + int iov_byte_offset;
    + int copy;
    + dma_cookie_t dma_cookie = 0;
    + int iovec_idx;
    + int page_idx;
    +
    + if (!chan)
    + return memcpy_toiovec(iov, kdata, len);
    +
    + /* -> kernel copies (e.g. smbfs) */
    + if (!pinned_list)
    + return dma_memcpy_to_kernel_iovec(chan, iov, kdata, len);
    +
    + iovec_idx = 0;
    + while (iovec_idx < pinned_list->nr_iovecs) {
    + struct dma_page_list *page_list;
    +
    + /* skip already used-up iovecs */
    + while (!iov[iovec_idx].iov_len)
    + iovec_idx++;
    +
    + page_list = &pinned_list->page_list[iovec_idx];
    +
    + iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
    + page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
    + - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
    +
    + /* break up copies to not cross page boundary */
    + while (iov[iovec_idx].iov_len) {
    + copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
    + copy = min_t(int, copy, iov[iovec_idx].iov_len);
    +
    + dma_cookie = dma_async_memcpy_buf_to_pg(chan,
    + page_list->pages[page_idx],
    + iov_byte_offset,
    + kdata,
    + copy);
    +
    + len -= copy;
    + iov[iovec_idx].iov_len -= copy;
    + iov[iovec_idx].iov_base += copy;
    +
    + if (!len)
    + return dma_cookie;
    +
    + kdata += copy;
    + iov_byte_offset = 0;
    + page_idx++;
    + }
    + iovec_idx++;
    + }
    +
    + /* really bad if we ever run out of iovecs */
    + BUG();
    + return -EFAULT;
    +}
    +
    +dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
    + struct dma_pinned_list *pinned_list, struct page *page,
    + unsigned int offset, size_t len)
    +{
    + int iov_byte_offset;
    + int copy;
    + dma_cookie_t dma_cookie = 0;
    + int iovec_idx;
    + int page_idx;
    + int err;
    +
    + /* this needs as-yet-unimplemented buf-to-buff, so punt. */
    + /* TODO: use dma for this */
    + if (!chan || !pinned_list) {
    + u8 *vaddr = kmap(page);
    + err = memcpy_toiovec(iov, vaddr + offset, len);
    + kunmap(page);
    + return err;
    + }
    +
    + iovec_idx = 0;
    + while (iovec_idx < pinned_list->nr_iovecs) {
    + struct dma_page_list *page_list;
    +
    + /* skip already used-up iovecs */
    + while (!iov[iovec_idx].iov_len)
    + iovec_idx++;
    +
    + page_list = &pinned_list->page_list[iovec_idx];
    +
    + iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
    + page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
    + - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
    +
    + /* break up copies to not cross page boundary */
    + while (iov[iovec_idx].iov_len) {
    + copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
    + copy = min_t(int, copy, iov[iovec_idx].iov_len);
    +
    + dma_cookie = dma_async_memcpy_pg_to_pg(chan,
    + page_list->pages[page_idx],
    + iov_byte_offset,
    + page,
    + offset,
    + copy);
    +
    + len -= copy;
    + iov[iovec_idx].iov_len -= copy;
    + iov[iovec_idx].iov_base += copy;
    +
    + if (!len)
    + return dma_cookie;
    +
    + offset += copy;
    + iov_byte_offset = 0;
    + page_idx++;
    + }
    + iovec_idx++;
    + }
    +
    + /* really bad if we ever run out of iovecs */
    + BUG();
    + return -EFAULT;
    +}
    diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
    index 3078154..78b236c 100644
    --- a/include/linux/dmaengine.h
    +++ b/include/linux/dmaengine.h
    @@ -333,5 +333,27 @@ static inline enum dma_status dma_async_
    int dma_async_device_register(struct dma_device *device);
    void dma_async_device_unregister(struct dma_device *device);

    +/* --- Helper iov-locking functions --- */
    +
    +struct dma_page_list {
    + char *base_address;
    + int nr_pages;
    + struct page **pages;
    +};
    +
    +struct dma_pinned_list {
    + int nr_iovecs;
    + struct dma_page_list page_list[0];
    +};
    +
    +struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len);
    +void dma_unpin_iovec_pages(struct dma_pinned_list* pinned_list);
    +
    +dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
    + struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len);
    +dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
    + struct dma_pinned_list *pinned_list, struct page *page,
    + unsigned int offset, size_t len);
    +
    #endif /* CONFIG_DMA_ENGINE */
    #endif /* DMAENGINE_H */
    diff --git a/include/net/netdma.h b/include/net/netdma.h
    index cbfe89d..19760eb 100644
    --- a/include/net/netdma.h
    +++ b/include/net/netdma.h
    @@ -23,6 +23,7 @@
    #include <linux/config.h>
    #ifdef CONFIG_NET_DMA
    #include <linux/dmaengine.h>
    +#include <linux/skbuff.h>

    static inline struct dma_chan *get_softnet_dma(void)
    {
    @@ -34,5 +35,10 @@ static inline struct dma_chan *get_softn
    rcu_read_unlock();
    return chan;
    }
    +
    +int dma_skb_copy_datagram_iovec(struct dma_chan* chan,
    + const struct sk_buff *skb, int offset, struct iovec *to,
    + size_t len, struct dma_pinned_list *pinned_list);
    +
    #endif /* CONFIG_NET_DMA */
    #endif /* NETDMA_H */
    diff --git a/net/core/Makefile b/net/core/Makefile
    index 79fe12c..e9bd246 100644
    --- a/net/core/Makefile
    +++ b/net/core/Makefile
    @@ -16,3 +16,4 @@ obj-$(CONFIG_NET_DIVERT) += dv.o
    obj-$(CONFIG_NET_PKTGEN) += pktgen.o
    obj-$(CONFIG_WIRELESS_EXT) += wireless.o
    obj-$(CONFIG_NETPOLL) += netpoll.o
    +obj-$(CONFIG_NET_DMA) += user_dma.o
    diff --git a/net/core/user_dma.c b/net/core/user_dma.c
    new file mode 100644
    index 0000000..9eee91b
    --- /dev/null
    +++ b/net/core/user_dma.c
    @@ -0,0 +1,127 @@
    +/*
    + * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
    + * Portions based on net/core/datagram.c and copyrighted by their authors.
    + *
    + * This program is free software; you can redistribute it and/or modify it
    + * under the terms of the GNU General Public License as published by the Free
    + * Software Foundation; either version 2 of the License, or (at your option)
    + * any later version.
    + *
    + * This program is distributed in the hope that it will be useful, but WITHOUT
    + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
    + * more details.
    + *
    + * You should have received a copy of the GNU General Public License along with
    + * this program; if not, write to the Free Software Foundation, Inc., 59
    + * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
    + *
    + * The full GNU General Public License is included in this distribution in the
    + * file called COPYING.
    + */
    +
    +/*
    + * This code allows the net stack to make use of a DMA engine for
    + * skb to iovec copies.
    + */
    +
    +#include <linux/dmaengine.h>
    +#include <linux/socket.h>
    +#include <linux/rtnetlink.h> /* for BUG_TRAP */
    +#include <net/tcp.h>
    +
    +/**
    + * dma_skb_copy_datagram_iovec - Copy a datagram to an iovec.
    + * @skb - buffer to copy
    + * @offset - offset in the buffer to start copying from
    + * @iovec - io vector to copy to
    + * @len - amount of data to copy from buffer to iovec
    + * @pinned_list - locked iovec buffer data
    + *
    + * Note: the iovec is modified during the copy.
    + */
    +int dma_skb_copy_datagram_iovec(struct dma_chan *chan,
    + struct sk_buff *skb, int offset, struct iovec *to,
    + size_t len, struct dma_pinned_list *pinned_list)
    +{
    + int start = skb_headlen(skb);
    + int i, copy = start - offset;
    + dma_cookie_t cookie = 0;
    +
    + /* Copy header. */
    + if (copy > 0) {
    + if (copy > len)
    + copy = len;
    + cookie = dma_memcpy_to_iovec(chan, to, pinned_list,
    + skb->data + offset, copy);
    + if (cookie < 0)
    + goto fault;
    + len -= copy;
    + if (len == 0)
    + goto end;
    + offset += copy;
    + }
    +
    + /* Copy paged appendix. Hmm... why does this look so complicated? */
    + for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
    + int end;
    +
    + BUG_TRAP(start <= offset + len);
    +
    + end = start + skb_shinfo(skb)->frags[i].size;
    + copy = end - offset;
    + if ((copy = end - offset) > 0) {
    + skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
    + struct page *page = frag->page;
    +
    + if (copy > len)
    + copy = len;
    +
    + cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
    + frag->page_offset + offset - start, copy);
    + if (cookie < 0)
    + goto fault;
    + len -= copy;
    + if (len == 0)
    + goto end;
    + offset += copy;
    + }
    + start = end;
    + }
    +
    + if (skb_shinfo(skb)->frag_list) {
    + struct sk_buff *list = skb_shinfo(skb)->frag_list;
    +
    + for (; list; list = list->next) {
    + int end;
    +
    + BUG_TRAP(start <= offset + len);
    +
    + end = start + list->len;
    + copy = end - offset;
    + if (copy > 0) {
    + if (copy > len)
    + copy = len;
    + cookie = dma_skb_copy_datagram_iovec(chan, list,
    + offset - start, to, copy,
    + pinned_list);
    + if (cookie < 0)
    + goto fault;
    + len -= copy;
    + if (len == 0)
    + goto end;
    + offset += copy;
    + }
    + start = end;
    + }
    + }
    +
    +end:
    + if (!len) {
    + skb->dma_cookie = cookie;
    + return cookie;
    + }
    +
    +fault:
    + return -EFAULT;
    +}
    -
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