Remove old lguest I/O infrrasructure.

This patch gets rid of the old lguest host I/O infrastructure and
replaces it with a single hypercall "LHCALL_NOTIFY" which takes an
address.

The main change is the removal of io.c: that mainly did inter-guest
I/O, which virtio doesn't yet support.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

6 files changed, 19 insertions, 715 deletions

diff --git a/drivers/lguest/Makefile b/drivers/lguest/Makefile
index 8c28236ee1ae..a63f75dc41a1 100644
--- a/drivers/lguest/Makefile
+++ b/drivers/lguest/Makefile
@@ -1,7 +1,7 @@
 # Host requires the other files, which can be a module.
 obj-$(CONFIG_LGUEST)    += lg.o
 lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \
-        segments.o io.o lguest_user.o
+        segments.o lguest_user.o
 
 lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o
 
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 41b26e592d38..3aec29ec7715 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -202,13 +202,12 @@ int run_guest(struct lguest *lg, unsigned long __user *user)
                 if (lg->hcall)
                         do_hypercalls(lg);
 
-                /* It's possible the Guest did a SEND_DMA hypercall to the
+                /* It's possible the Guest did a NOTIFY hypercall to the
                  * Launcher, in which case we return from the read() now. */
-                if (lg->dma_is_pending) {
-                        if (put_user(lg->pending_dma, user) ||
-                            put_user(lg->pending_key, user+1))
+                if (lg->pending_notify) {
+                        if (put_user(lg->pending_notify, user))
                                 return -EFAULT;
-                        return sizeof(unsigned long)*2;
+                        return sizeof(lg->pending_notify);
                 }
 
                 /* Check for signals */
@@ -288,9 +287,6 @@ static int __init init(void)
         if (err)
                 goto unmap;
 
-        /* The I/O subsystem needs some things initialized. */
-        lguest_io_init();
-
         /* We might need to reserve an interrupt vector. */
         err = init_interrupts();
         if (err)
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index 13b5f2f813de..3a53788ba450 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -60,22 +60,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
                 else
                         guest_pagetable_flush_user(lg);
                 break;
-        case LHCALL_BIND_DMA:
-                /* BIND_DMA really wants four arguments, but it's the only call
-                 * which does.  So the Guest packs the number of buffers and
-                 * the interrupt number into the final argument, and we decode
-                 * it here.  This can legitimately fail, since we currently
-                 * place a limit on the number of DMA pools a Guest can have.
-                 * So we return true or false from this call. */
-                args->arg0 = bind_dma(lg, args->arg1, args->arg2,
-                                     args->arg3 >> 8, args->arg3 & 0xFF);
-                break;
 
         /* All these calls simply pass the arguments through to the right
          * routines. */
-        case LHCALL_SEND_DMA:
-                send_dma(lg, args->arg1, args->arg2);
-                break;
         case LHCALL_NEW_PGTABLE:
                 guest_new_pagetable(lg, args->arg1);
                 break;
@@ -99,6 +86,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
                 /* Similarly, this sets the halted flag for run_guest(). */
                 lg->halted = 1;
                 break;
+        case LHCALL_NOTIFY:
+                lg->pending_notify = args->arg1;
+                break;
         default:
                 if (lguest_arch_do_hcall(lg, args))
                         kill_guest(lg, "Bad hypercall %li\n", args->arg0);
@@ -156,9 +146,9 @@ static void do_async_hcalls(struct lguest *lg)
                         break;
                 }
 
-                /* Stop doing hypercalls if we've just done a DMA to the
-                 * Launcher: it needs to service this first. */
-                if (lg->dma_is_pending)
+                /* Stop doing hypercalls if they want to notify the Launcher:
+                 * it needs to service this first. */
+                if (lg->pending_notify)
                         break;
         }
 }
@@ -220,9 +210,9 @@ void do_hypercalls(struct lguest *lg)
         do_async_hcalls(lg);
 
         /* If we stopped reading the hypercall ring because the Guest did a
-         * SEND_DMA to the Launcher, we want to return now.  Otherwise we do
+         * NOTIFY to the Launcher, we want to return now.  Otherwise we do
          * the hypercall. */
-        if (!lg->dma_is_pending) {
+        if (!lg->pending_notify) {
                 do_hcall(lg, lg->hcall);
                 /* Tricky point: we reset the hcall pointer to mark the
                  * hypercall as "done".  We use the hcall pointer rather than
diff --git a/drivers/lguest/io.c b/drivers/lguest/io.c
deleted file mode 100644
index 0e842e9caf68..000000000000
--- a/drivers/lguest/io.c
+++ /dev/null
@@ -1,628 +0,0 @@
-/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest
- * to talk to the Launcher or directly to another Guest.  It uses familiar
- * concepts of DMA and interrupts, plus some neat code stolen from
- * futexes... :*/
-
-/* Copyright (C) 2006 Rusty Russell IBM Corporation
- *
- *  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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
- */
-#include <linux/types.h>
-#include <linux/futex.h>
-#include <linux/jhash.h>
-#include <linux/mm.h>
-#include <linux/highmem.h>
-#include <linux/uaccess.h>
-#include "lg.h"
-
-/*L:300
- * I/O
- *
- * Getting data in and out of the Guest is quite an art.  There are numerous
- * ways to do it, and they all suck differently.  We try to keep things fairly
- * close to "real" hardware so our Guest's drivers don't look like an alien
- * visitation in the middle of the Linux code, and yet make sure that Guests
- * can talk directly to other Guests, not just the Launcher.
- *
- * To do this, the Guest gives us a key when it binds or sends DMA buffers.
- * The key corresponds to a "physical" address inside the Guest (ie. a virtual
- * address inside the Launcher process).  We don't, however, use this key
- * directly.
- *
- * We want Guests which share memory to be able to DMA to each other: two
- * Launchers can mmap memory the same file, then the Guests can communicate.
- * Fortunately, the futex code provides us with a way to get a "union
- * futex_key" corresponding to the memory lying at a virtual address: if the
- * two processes share memory, the "union futex_key" for that memory will match
- * even if the memory is mapped at different addresses in each.  So we always
- * convert the keys to "union futex_key"s to compare them.
- *
- * Before we dive into this though, we need to look at another set of helper
- * routines used throughout the Host kernel code to access Guest memory.
- :*/
-static struct list_head dma_hash[61];
-
-/* An unfortunate side effect of the Linux double-linked list implementation is
- * that there's no good way to statically initialize an array of linked
- * lists. */
-void lguest_io_init(void)
-{
-        unsigned int i;
-
-        for (i = 0; i < ARRAY_SIZE(dma_hash); i++)
-                INIT_LIST_HEAD(&dma_hash[i]);
-}
-
-/* FIXME: allow multi-page lengths. */
-static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma)
-{
-        unsigned int i;
-
-        for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
-                if (!dma->len[i])
-                        return 1;
-                if (!lguest_address_ok(lg, dma->addr[i], dma->len[i]))
-                        goto kill;
-                if (dma->len[i] > PAGE_SIZE)
-                        goto kill;
-                /* We could do over a page, but is it worth it? */
-                if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE)
-                        goto kill;
-        }
-        return 1;
-
-kill:
-        kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]);
-        return 0;
-}
-
-/*L:330 This is our hash function, using the wonderful Jenkins hash.
- *
- * The futex key is a union with three parts: an unsigned long word, a pointer,
- * and an int "offset".  We could use jhash_2words() which takes three u32s.
- * (Ok, the hash functions are great: the naming sucks though).
- *
- * It's nice to be portable to 64-bit platforms, so we use the more generic
- * jhash2(), which takes an array of u32, the number of u32s, and an initial
- * u32 to roll in.  This is uglier, but breaks down to almost the same code on
- * 32-bit platforms like this one.
- *
- * We want a position in the array, so we modulo ARRAY_SIZE(dma_hash) (ie. 61).
- */
-static unsigned int hash(const union futex_key *key)
-{
-        return jhash2((u32*)&key->both.word,
-                      (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
-                      key->both.offset)
-                % ARRAY_SIZE(dma_hash);
-}
-
-/* This is a convenience routine to compare two keys.  It's a much bemoaned C
- * weakness that it doesn't allow '==' on structures or unions, so we have to
- * open-code it like this. */
-static inline int key_eq(const union futex_key *a, const union futex_key *b)
-{
-        return (a->both.word == b->both.word
-                && a->both.ptr == b->both.ptr
-                && a->both.offset == b->both.offset);
-}
-
-/*L:360 OK, when we need to actually free up a Guest's DMA array we do several
- * things, so we have a convenient function to do it.
- *
- * The caller must hold a read lock on dmainfo owner's current->mm->mmap_sem
- * for the drop_futex_key_refs(). */
-static void unlink_dma(struct lguest_dma_info *dmainfo)
-{
-        /* You locked this too, right? */
-        BUG_ON(!mutex_is_locked(&lguest_lock));
-        /* This is how we know that the entry is free. */
-        dmainfo->interrupt = 0;
-        /* Remove it from the hash table. */
-        list_del(&dmainfo->list);
-        /* Drop the references we were holding (to the inode or mm). */
-        drop_futex_key_refs(&dmainfo->key);
-}
-
-/*L:350 This is the routine which we call when the Guest asks to unregister a
- * DMA array attached to a given key.  Returns true if the array was found. */
-static int unbind_dma(struct lguest *lg,
-                      const union futex_key *key,
-                      unsigned long dmas)
-{
-        int i, ret = 0;
-
-        /* We don't bother with the hash table, just look through all this
-         * Guest's DMA arrays. */
-        for (i = 0; i < LGUEST_MAX_DMA; i++) {
-                /* In theory it could have more than one array on the same key,
-                 * or one array on multiple keys, so we check both */
-                if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) {
-                        unlink_dma(&lg->dma[i]);
-                        ret = 1;
-                        break;
-                }
-        }
-        return ret;
-}
-
-/*L:340 BIND_DMA: this is the hypercall which sets up an array of "struct
- * lguest_dma" for receiving I/O.
- *
- * The Guest wants to bind an array of "struct lguest_dma"s to a particular key
- * to receive input.  This only happens when the Guest is setting up a new
- * device, so it doesn't have to be very fast.
- *
- * It returns 1 on a successful registration (it can fail if we hit the limit
- * of registrations for this Guest).
- */
-int bind_dma(struct lguest *lg,
-             unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt)
-{
-        unsigned int i;
-        int ret = 0;
-        union futex_key key;
-        /* Futex code needs the mmap_sem. */
-        struct rw_semaphore *fshared = &current->mm->mmap_sem;
-
-        /* Invalid interrupt?  (We could kill the guest here). */
-        if (interrupt >= LGUEST_IRQS)
-                return 0;
-
-        /* We need to grab the Big Lguest Lock, because other Guests may be
-         * trying to look through this Guest's DMAs to send something while
-         * we're doing this. */
-        mutex_lock(&lguest_lock);
-        down_read(fshared);
-        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
-                kill_guest(lg, "bad dma key %#lx", ukey);
-                goto unlock;
-        }
-
-        /* We want to keep this key valid once we drop mmap_sem, so we have to
-         * hold a reference. */
-        get_futex_key_refs(&key);
-
-        /* If the Guest specified an interrupt of 0, that means they want to
-         * unregister this array of "struct lguest_dma"s. */
-        if (interrupt == 0)
-                ret = unbind_dma(lg, &key, dmas);
-        else {
-                /* Look through this Guest's dma array for an unused entry. */
-                for (i = 0; i < LGUEST_MAX_DMA; i++) {
-                        /* If the interrupt is non-zero, the entry is already
-                         * used. */
-                        if (lg->dma[i].interrupt)
-                                continue;
-
-                        /* OK, a free one!  Fill on our details. */
-                        lg->dma[i].dmas = dmas;
-                        lg->dma[i].num_dmas = numdmas;
-                        lg->dma[i].next_dma = 0;
-                        lg->dma[i].key = key;
-                        lg->dma[i].owner = lg;
-                        lg->dma[i].interrupt = interrupt;
-
-                        /* Now we add it to the hash table: the position
-                         * depends on the futex key that we got. */
-                        list_add(&lg->dma[i].list, &dma_hash[hash(&key)]);
-                        /* Success! */
-                        ret = 1;
-                        goto unlock;
-                }
-        }
-        /* If we didn't find a slot to put the key in, drop the reference
-         * again. */
-        drop_futex_key_refs(&key);
-unlock:
-        /* Unlock and out. */
-        up_read(fshared);
-        mutex_unlock(&lguest_lock);
-        return ret;
-}
-
-/*L:385 Note that our routines to access a different Guest's memory are called
- * lgread_other() and lgwrite_other(): these names emphasize that they are only
- * used when the Guest is *not* the current Guest.
- *
- * The interface for copying from another process's memory is called
- * access_process_vm(), with a final argument of 0 for a read, and 1 for a
- * write.
- *
- * We need lgread_other() to read the destination Guest's "struct lguest_dma"
- * array. */
-static int lgread_other(struct lguest *lg,
-                        void *buf, u32 addr, unsigned bytes)
-{
-        if (!lguest_address_ok(lg, addr, bytes)
-            || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
-                                 buf, bytes, 0) != bytes) {
-                memset(buf, 0, bytes);
-                kill_guest(lg, "bad address in registered DMA struct");
-                return 0;
-        }
-        return 1;
-}
-
-/* "lgwrite()" to another Guest: used to update the destination "used_len" once
- * we've transferred data into the buffer. */
-static int lgwrite_other(struct lguest *lg, u32 addr,
-                         const void *buf, unsigned bytes)
-{
-        if (!lguest_address_ok(lg, addr, bytes)
-            || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
-                                 (void *)buf, bytes, 1) != bytes) {
-                kill_guest(lg, "bad address writing to registered DMA");
-                return 0;
-        }
-        return 1;
-}
-
-/*L:400 This is the generic engine which copies from a source "struct
- * lguest_dma" from this Guest into another Guest's "struct lguest_dma".  The
- * destination Guest's pages have already been mapped, as contained in the
- * pages array.
- *
- * If you're wondering if there's a nice "copy from one process to another"
- * routine, so was I.  But Linux isn't really set up to copy between two
- * unrelated processes, so we have to write it ourselves.
- */
-static u32 copy_data(struct lguest *srclg,
-                     const struct lguest_dma *src,
-                     const struct lguest_dma *dst,
-                     struct page *pages[])
-{
-        unsigned int totlen, si, di, srcoff, dstoff;
-        void *maddr = NULL;
-
-        /* We return the total length transferred. */
-        totlen = 0;
-
-        /* We keep indexes into the source and destination "struct lguest_dma",
-         * and an offset within each region. */
-        si = di = 0;
-        srcoff = dstoff = 0;
-
-        /* We loop until the source or destination is exhausted. */
-        while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si]
-               && di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) {
-                /* We can only transfer the rest of the src buffer, or as much
-                 * as will fit into the destination buffer. */
-                u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff);
-
-                /* For systems using "highmem" we need to use kmap() to access
-                 * the page we want.  We often use the same page over and over,
-                 * so rather than kmap() it on every loop, we set the maddr
-                 * pointer to NULL when we need to move to the next
-                 * destination page. */
-                if (!maddr)
-                        maddr = kmap(pages[di]);
-
-                /* Copy directly from (this Guest's) source address to the
-                 * destination Guest's kmap()ed buffer.  Note that maddr points
-                 * to the start of the page: we need to add the offset of the
-                 * destination address and offset within the buffer. */
-
-                /* FIXME: This is not completely portable.  I looked at
-                 * copy_to_user_page(), and some arch's seem to need special
-                 * flushes.  x86 is fine. */
-                if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
-                                   srclg->mem_base+src->addr[si], len) != 0) {
-                        /* If a copy failed, it's the source's fault. */
-                        kill_guest(srclg, "bad address in sending DMA");
-                        totlen = 0;
-                        break;
-                }
-
-                /* Increment the total and src & dst offsets */
-                totlen += len;
-                srcoff += len;
-                dstoff += len;
-
-                /* Presumably we reached the end of the src or dest buffers: */
-                if (srcoff == src->len[si]) {
-                        /* Move to the next buffer at offset 0 */
-                        si++;
-                        srcoff = 0;
-                }
-                if (dstoff == dst->len[di]) {
-                        /* We need to unmap that destination page and reset
-                         * maddr ready for the next one. */
-                        kunmap(pages[di]);
-                        maddr = NULL;
-                        di++;
-                        dstoff = 0;
-                }
-        }
-
-        /* If we still had a page mapped at the end, unmap now. */
-        if (maddr)
-                kunmap(pages[di]);
-
-        return totlen;
-}
-
-/*L:390 This is how we transfer a "struct lguest_dma" from the source Guest
- * (the current Guest which called SEND_DMA) to another Guest. */
-static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src,
-                  struct lguest *dstlg, const struct lguest_dma *dst)
-{
-        int i;
-        u32 ret;
-        struct page *pages[LGUEST_MAX_DMA_SECTIONS];
-
-        /* We check that both source and destination "struct lguest_dma"s are
-         * within the bounds of the source and destination Guests */
-        if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src))
-                return 0;
-
-        /* We need to map the pages which correspond to each parts of
-         * destination buffer. */
-        for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
-                if (dst->len[i] == 0)
-                        break;
-                /* get_user_pages() is a complicated function, especially since
-                 * we only want a single page.  But it works, and returns the
-                 * number of pages.  Note that we're holding the destination's
-                 * mmap_sem, as get_user_pages() requires. */
-                if (get_user_pages(dstlg->tsk, dstlg->mm,
-                                   (unsigned long)dstlg->mem_base+dst->addr[i],
-                                   1, 1, 1, pages+i, NULL)
-                    != 1) {
-                        /* This means the destination gave us a bogus buffer */
-                        kill_guest(dstlg, "Error mapping DMA pages");
-                        ret = 0;
-                        goto drop_pages;
-                }
-        }
-
-        /* Now copy the data until we run out of src or dst. */
-        ret = copy_data(srclg, src, dst, pages);
-
-drop_pages:
-        while (--i >= 0)
-                put_page(pages[i]);
-        return ret;
-}
-
-/*L:380 Transferring data from one Guest to another is not as simple as I'd
- * like.  We've found the "struct lguest_dma_info" bound to the same address as
- * the send, we need to copy into it.
- *
- * This function returns true if the destination array was empty. */
-static int dma_transfer(struct lguest *srclg,
-                        unsigned long udma,
-                        struct lguest_dma_info *dst)
-{
-        struct lguest_dma dst_dma, src_dma;
-        struct lguest *dstlg;
-        u32 i, dma = 0;
-
-        /* From the "struct lguest_dma_info" we found in the hash, grab the
-         * Guest. */
-        dstlg = dst->owner;
-        /* Read in the source "struct lguest_dma" handed to SEND_DMA. */
-        lgread(srclg, &src_dma, udma, sizeof(src_dma));
-
-        /* We need the destination's mmap_sem, and we already hold the source's
-         * mmap_sem for the futex key lookup.  Normally this would suggest that
-         * we could deadlock if the destination Guest was trying to send to
-         * this source Guest at the same time, which is another reason that all
-         * I/O is done under the big lguest_lock. */
-        down_read(&dstlg->mm->mmap_sem);
-
-        /* Look through the destination DMA array for an available buffer. */
-        for (i = 0; i < dst->num_dmas; i++) {
-                /* We keep a "next_dma" pointer which often helps us avoid
-                 * looking at lots of previously-filled entries. */
-                dma = (dst->next_dma + i) % dst->num_dmas;
-                if (!lgread_other(dstlg, &dst_dma,
-                                  dst->dmas + dma * sizeof(struct lguest_dma),
-                                  sizeof(dst_dma))) {
-                        goto fail;
-                }
-                if (!dst_dma.used_len)
-                        break;
-        }
-
-        /* If we found a buffer, we do the actual data copy. */
-        if (i != dst->num_dmas) {
-                unsigned long used_lenp;
-                unsigned int ret;
-
-                ret = do_dma(srclg, &src_dma, dstlg, &dst_dma);
-                /* Put used length in the source "struct lguest_dma"'s used_len
-                 * field.  It's a little tricky to figure out where that is,
-                 * though. */
-                lgwrite_u32(srclg,
-                            udma+offsetof(struct lguest_dma, used_len), ret);
-                /* Tranferring 0 bytes is OK if the source buffer was empty. */
-                if (ret == 0 && src_dma.len[0] != 0)
-                        goto fail;
-
-                /* The destination Guest might be running on a different CPU:
-                 * we have to make sure that it will see the "used_len" field
-                 * change to non-zero *after* it sees the data we copied into
-                 * the buffer.  Hence a write memory barrier. */
-                wmb();
-                /* Figuring out where the destination's used_len field for this
-                 * "struct lguest_dma" in the array is also a little ugly. */
-                used_lenp = dst->dmas
-                        + dma * sizeof(struct lguest_dma)
-                        + offsetof(struct lguest_dma, used_len);
-                lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret));
-                /* Move the cursor for next time. */
-                dst->next_dma++;
-        }
-        up_read(&dstlg->mm->mmap_sem);
-
-        /* We trigger the destination interrupt, even if the destination was
-         * empty and we didn't transfer anything: this gives them a chance to
-         * wake up and refill. */
-        set_bit(dst->interrupt, dstlg->irqs_pending);
-        /* Wake up the destination process. */
-        wake_up_process(dstlg->tsk);
-        /* If we passed the last "struct lguest_dma", the receive had no
-         * buffers left. */
-        return i == dst->num_dmas;
-
-fail:
-        up_read(&dstlg->mm->mmap_sem);
-        return 0;
-}
-
-/*L:370 This is the counter-side to the BIND_DMA hypercall; the SEND_DMA
- * hypercall.  We find out who's listening, and send to them. */
-void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma)
-{
-        union futex_key key;
-        int empty = 0;
-        struct rw_semaphore *fshared = &current->mm->mmap_sem;
-
-again:
-        mutex_lock(&lguest_lock);
-        down_read(fshared);
-        /* Get the futex key for the key the Guest gave us */
-        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
-                kill_guest(lg, "bad sending DMA key");
-                goto unlock;
-        }
-        /* Since the key must be a multiple of 4, the futex key uses the lower
-         * bit of the "offset" field (which would always be 0) to indicate a
-         * mapping which is shared with other processes (ie. Guests). */
-        if (key.shared.offset & 1) {
-                struct lguest_dma_info *i;
-                /* Look through the hash for other Guests. */
-                list_for_each_entry(i, &dma_hash[hash(&key)], list) {
-                        /* Don't send to ourselves (would deadlock). */
-                        if (i->owner->mm == lg->mm)
-                                continue;
-                        if (!key_eq(&key, &i->key))
-                                continue;
-
-                        /* If dma_transfer() tells us the destination has no
-                         * available buffers, we increment "empty". */
-                        empty += dma_transfer(lg, udma, i);
-                        break;
-                }
-                /* If the destination is empty, we release our locks and
-                 * give the destination Guest a brief chance to restock. */
-                if (empty == 1) {
-                        /* Give any recipients one chance to restock. */
-                        up_read(&current->mm->mmap_sem);
-                        mutex_unlock(&lguest_lock);
-                        /* Next time, we won't try again. */
-                        empty++;
-                        goto again;
-                }
-        } else {
-                /* Private mapping: Guest is sending to its Launcher.  We set
-                 * the "dma_is_pending" flag so that the main loop will exit
-                 * and the Launcher's read() from /dev/lguest will return. */
-                lg->dma_is_pending = 1;
-                lg->pending_dma = udma;
-                lg->pending_key = ukey;
-        }
-unlock:
-        up_read(fshared);
-        mutex_unlock(&lguest_lock);
-}
-/*:*/
-
-void release_all_dma(struct lguest *lg)
-{
-        unsigned int i;
-
-        BUG_ON(!mutex_is_locked(&lguest_lock));
-
-        down_read(&lg->mm->mmap_sem);
-        for (i = 0; i < LGUEST_MAX_DMA; i++) {
-                if (lg->dma[i].interrupt)
-                        unlink_dma(&lg->dma[i]);
-        }
-        up_read(&lg->mm->mmap_sem);
-}
-
-/*M:007 We only return a single DMA buffer to the Launcher, but it would be
- * more efficient to return a pointer to the entire array of DMA buffers, which
- * it can cache and choose one whenever it wants.
- *
- * Currently the Launcher uses a write to /dev/lguest, and the return value is
- * the address of the DMA structure with the interrupt number placed in
- * dma->used_len.  If we wanted to return the entire array, we need to return
- * the address, array size and interrupt number: this seems to require an
- * ioctl(). :*/
-
-/*L:320 This routine looks for a DMA buffer registered by the Guest on the
- * given key (using the BIND_DMA hypercall). */
-unsigned long get_dma_buffer(struct lguest *lg,
-                             unsigned long ukey, unsigned long *interrupt)
-{
-        unsigned long ret = 0;
-        union futex_key key;
-        struct lguest_dma_info *i;
-        struct rw_semaphore *fshared = &current->mm->mmap_sem;
-
-        /* Take the Big Lguest Lock to stop other Guests sending this Guest DMA
-         * at the same time. */
-        mutex_lock(&lguest_lock);
-        /* To match between Guests sharing the same underlying memory we steal
-         * code from the futex infrastructure.  This requires that we hold the
-         * "mmap_sem" for our process (the Launcher), and pass it to the futex
-         * code. */
-        down_read(fshared);
-
-        /* This can fail if it's not a valid address, or if the address is not
-         * divisible by 4 (the futex code needs that, we don't really). */
-        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
-                kill_guest(lg, "bad registered DMA buffer");
-                goto unlock;
-        }
-        /* Search the hash table for matching entries (the Launcher can only
-         * send to its own Guest for the moment, so the entry must be for this
-         * Guest) */
-        list_for_each_entry(i, &dma_hash[hash(&key)], list) {
-                if (key_eq(&key, &i->key) && i->owner == lg) {
-                        unsigned int j;
-                        /* Look through the registered DMA array for an
-                         * available buffer. */
-                        for (j = 0; j < i->num_dmas; j++) {
-                                struct lguest_dma dma;
-
-                                ret = i->dmas + j * sizeof(struct lguest_dma);
-                                lgread(lg, &dma, ret, sizeof(dma));
-                                if (dma.used_len == 0)
-                                        break;
-                        }
-                        /* Store the interrupt the Guest wants when the buffer
-                         * is used. */
-                        *interrupt = i->interrupt;
-                        break;
-                }
-        }
-unlock:
-        up_read(fshared);
-        mutex_unlock(&lguest_lock);
-        return ret;
-}
-/*:*/
-
-/*L:410 This really has completed the Launcher.  Not only have we now finished
- * the longest chapter in our journey, but this also means we are over halfway
- * through!
- *
- * Enough prevaricating around the bush: it is time for us to dive into the
- * core of the Host, in "make Host".
- */
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index e4845d7f0688..4d45b7036e82 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -5,7 +5,6 @@
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/stringify.h>
-#include <linux/futex.h>
 #include <linux/lguest.h>
 #include <linux/lguest_launcher.h>
 #include <linux/wait.h>
@@ -17,17 +16,6 @@
 void free_pagetables(void);
 int init_pagetables(struct page **switcher_page, unsigned int pages);
 
-struct lguest_dma_info
-{
-        struct list_head list;
-        union futex_key key;
-        unsigned long dmas;
-        struct lguest *owner;
-        u16 next_dma;
-        u16 num_dmas;
-        u8 interrupt;   /* 0 when not registered */
-};
-
 struct pgdir
 {
         unsigned long gpgdir;
@@ -90,15 +78,11 @@ struct lguest
         struct task_struct *wake;
 
         unsigned long noirq_start, noirq_end;
-        int dma_is_pending;
-        unsigned long pending_dma; /* struct lguest_dma */
-        unsigned long pending_key; /* address they're sending to */
+        unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
 
         unsigned int stack_pages;
         u32 tsc_khz;
 
-        struct lguest_dma_info dma[LGUEST_MAX_DMA];
-
         /* Dead? */
         const char *dead;
 
@@ -184,15 +168,6 @@ extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
 int lguest_device_init(void);
 void lguest_device_remove(void);
 
-/* io.c: */
-void lguest_io_init(void);
-int bind_dma(struct lguest *lg,
-             unsigned long key, unsigned long udma, u16 numdmas, u8 interrupt);
-void send_dma(struct lguest *info, unsigned long key, unsigned long udma);
-void release_all_dma(struct lguest *lg);
-unsigned long get_dma_buffer(struct lguest *lg, unsigned long key,
-                             unsigned long *interrupt);
-
 /* hypercalls.c: */
 void do_hypercalls(struct lguest *lg);
 void write_timestamp(struct lguest *lg);
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index 61b177e1e649..ee405b38383d 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -2,37 +2,12 @@
  * controls and communicates with the Guest.  For example, the first write will
  * tell us the Guest's memory layout, pagetable, entry point and kernel address
  * offset.  A read will run the Guest until something happens, such as a signal
- * or the Guest doing a DMA out to the Launcher.  Writes are also used to get a
- * DMA buffer registered by the Guest and to send the Guest an interrupt. :*/
+ * or the Guest doing a NOTIFY out to the Launcher. :*/
 #include <linux/uaccess.h>
 #include <linux/miscdevice.h>
 #include <linux/fs.h>
 #include "lg.h"
 
-/*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a
- * DMA buffer.  This is done by writing LHREQ_GETDMA and the key to
- * /dev/lguest. */
-static long user_get_dma(struct lguest *lg, const unsigned long __user *input)
-{
-        unsigned long key, udma, irq;
-
-        /* Fetch the key they wrote to us. */
-        if (get_user(key, input) != 0)
-                return -EFAULT;
-        /* Look for a free Guest DMA buffer bound to that key. */
-        udma = get_dma_buffer(lg, key, &irq);
-        if (!udma)
-                return -ENOENT;
-
-        /* We need to tell the Launcher what interrupt the Guest expects after
-         * the buffer is filled.  We stash it in udma->used_len. */
-        lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq);
-
-        /* The (guest-physical) address of the DMA buffer is returned from
-         * the write(). */
-        return udma;
-}
-
 /*L:315 To force the Guest to stop running and return to the Launcher, the
  * Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest.  The
  * Launcher then writes LHREQ_BREAK and "0" to release the Waker. */
@@ -102,10 +77,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
                 return len;
         }
 
-        /* If we returned from read() last time because the Guest sent DMA,
+        /* If we returned from read() last time because the Guest notified,
          * clear the flag. */
-        if (lg->dma_is_pending)
-                lg->dma_is_pending = 0;
+        if (lg->pending_notify)
+                lg->pending_notify = 0;
 
         /* Run the Guest until something interesting happens. */
         return run_guest(lg, (unsigned long __user *)user);
@@ -216,7 +191,7 @@ unlock:
 /*L:010 The first operation the Launcher does must be a write.  All writes
  * start with a 32 bit number: for the first write this must be
  * LHREQ_INITIALIZE to set up the Guest.  After that the Launcher can use
- * writes of other values to get DMA buffers and send interrupts. */
+ * writes of other values to send interrupts. */
 static ssize_t write(struct file *file, const char __user *in,
                      size_t size, loff_t *off)
 {
@@ -245,8 +220,6 @@ static ssize_t write(struct file *file, const char __user *in,
         switch (req) {
         case LHREQ_INITIALIZE:
                 return initialize(file, input);
-        case LHREQ_GETDMA:
-                return user_get_dma(lg, input);
         case LHREQ_IRQ:
                 return user_send_irq(lg, input);
         case LHREQ_BREAK:
@@ -276,8 +249,6 @@ static int close(struct inode *inode, struct file *file)
         mutex_lock(&lguest_lock);
         /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
         hrtimer_cancel(&lg->hrt);
-        /* Free any DMA buffers the Guest had bound. */
-        release_all_dma(lg);
         /* Free up the shadow page tables for the Guest. */
         free_guest_pagetable(lg);
         /* Now all the memory cleanups are done, it's safe to release the