Linux Virtualization - Mar 2016 - [RFC PATCH V2 1/2] vhost: convert pre sorted vhost memory array to interval tree

This patch tries to implement an device IOTLB for vhost. This could be
used with for co-operation with userspace(qemu) implementation of
iommu for a secure DMA environment (DMAR) in guest.

The idea is simple. When vhost meets an IOTLB miss, it will request
the assistance of userspace to do the translation, this is done
through:

- Fill the translation request in a preset userspace address (This
  address is set through ioctl VHOST_SET_IOTLB_REQUEST_ENTRY).
- Notify userspace through eventfd (This eventfd was set through ioctl
  VHOST_SET_IOTLB_FD).

When userspace finishes the translation, it will update the vhost
IOTLB through VHOST_UPDATE_IOTLB ioctl. Userspace is also in charge of
snooping the IOTLB invalidation of IOMMU IOTLB and use
VHOST_UPDATE_IOTLB to invalidate the possible entry in vhost.

The codes were designed to be architecture independent. It should be
easily ported to any architecture.

Changes from V1:
- support any size/range of updating and invalidation through
  introducing the interval tree.
- convert from per device iotlb request to per virtqueue iotlb
  request, this solves the possible deadlock in V1.
- read/write permission check support.

Please review.

Thanks

Jason Wang (2):
  vhost: convert pre sorted vhost memory array to interval tree
  vhost: device IOTLB API

 drivers/vhost/net.c        |  14 +-
 drivers/vhost/vhost.c      | 427 +++++++++++++++++++++++++++++++++++----------
 drivers/vhost/vhost.h      |  42 ++++-
 fs/eventfd.c               |   3 +-
 include/uapi/linux/vhost.h |  35 ++++
 5 files changed, 419 insertions(+), 102 deletions(-)

-- 
2.5.0

Current pre-sorted memory region array has some limitations for future
device IOTLB conversion:

1) need extra work for adding and removing a single region, and it's
   expected to be slow because of sorting or memory re-allocation.
2) need extra work of removing a large range which may intersect
   several regions with different size.
3) need trick for a replacement policy like LRU

To overcome the above shortcomings, this patch convert it to interval
tree which can easily address the above issue with almost no extra
work.

The patch could be used for:

- Extend the current API and only let the userspace to send diffs of
  memory table.
- Simplify Device IOTLB implementation.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/net.c   |   8 +--
 drivers/vhost/vhost.c | 182 ++++++++++++++++++++++++++++----------------------
 drivers/vhost/vhost.h |  27 ++++++--
 3 files changed, 128 insertions(+), 89 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9eda69e..481db96 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -968,20 +968,20 @@ static long vhost_net_reset_owner(struct vhost_net *n)
 	struct socket *tx_sock = NULL;
 	struct socket *rx_sock = NULL;
 	long err;
-	struct vhost_memory *memory;
+	struct vhost_umem *umem;
 
 	mutex_lock(&n->dev.mutex);
 	err = vhost_dev_check_owner(&n->dev);
 	if (err)
 		goto done;
-	memory = vhost_dev_reset_owner_prepare();
-	if (!memory) {
+	umem = vhost_dev_reset_owner_prepare();
+	if (!umem) {
 		err = -ENOMEM;
 		goto done;
 	}
 	vhost_net_stop(n, &tx_sock, &rx_sock);
 	vhost_net_flush(n);
-	vhost_dev_reset_owner(&n->dev, memory);
+	vhost_dev_reset_owner(&n->dev, umem);
 	vhost_net_vq_reset(n);
 done:
 	mutex_unlock(&n->dev.mutex);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index ad2146a..32c35a9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -27,6 +27,7 @@
 #include <linux/cgroup.h>
 #include <linux/module.h>
 #include <linux/sort.h>
+#include <linux/interval_tree_generic.h>
 
 #include "vhost.h"
 
@@ -42,6 +43,10 @@ enum {
 #define vhost_used_event(vq) ((__virtio16 __user
*)&vq->avail->ring[vq->num])
 #define vhost_avail_event(vq) ((__virtio16 __user
*)&vq->used->ring[vq->num])
 
+INTERVAL_TREE_DEFINE(struct vhost_umem_node,
+		     rb, __u64, __subtree_last,
+		     START, LAST, , vhost_umem_interval_tree);
+
 #ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
 static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
 {
@@ -275,7 +280,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 	vq->call_ctx = NULL;
 	vq->call = NULL;
 	vq->log_ctx = NULL;
-	vq->memory = NULL;
+	vq->umem = NULL;
 	vq->is_le = virtio_legacy_is_little_endian();
 	vhost_vq_reset_user_be(vq);
 }
@@ -381,7 +386,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 	mutex_init(&dev->mutex);
 	dev->log_ctx = NULL;
 	dev->log_file = NULL;
-	dev->memory = NULL;
+	dev->umem = NULL;
 	dev->mm = NULL;
 	spin_lock_init(&dev->work_lock);
 	INIT_LIST_HEAD(&dev->work_list);
@@ -486,27 +491,36 @@ err_mm:
 }
 EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
 
-struct vhost_memory *vhost_dev_reset_owner_prepare(void)
+static void *vhost_kvzalloc(unsigned long size)
+{
+	void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
+
+	if (!n)
+		n = vzalloc(size);
+	return n;
+}
+
+struct vhost_umem *vhost_dev_reset_owner_prepare(void)
 {
-	return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
+	return vhost_kvzalloc(sizeof(struct vhost_umem));
 }
 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
 
 /* Caller should have device mutex */
-void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
+void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_umem *umem)
 {
 	int i;
 
 	vhost_dev_cleanup(dev, true);
 
 	/* Restore memory to default empty mapping. */
-	memory->nregions = 0;
-	dev->memory = memory;
+	INIT_LIST_HEAD(&umem->umem_list);
+	dev->umem = umem;
 	/* We don't need VQ locks below since vhost_dev_cleanup makes sure
 	 * VQs aren't running.
 	 */
 	for (i = 0; i < dev->nvqs; ++i)
-		dev->vqs[i]->memory = memory;
+		dev->vqs[i]->umem = umem;
 }
 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
 
@@ -523,6 +537,21 @@ void vhost_dev_stop(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 
+static void vhost_umem_clean(struct vhost_umem *umem)
+{
+	struct vhost_umem_node *node, *tmp;
+
+	if (!umem)
+		return;
+
+	list_for_each_entry_safe(node, tmp, &umem->umem_list, link) {
+		vhost_umem_interval_tree_remove(node, &umem->umem_tree);
+		list_del(&node->link);
+		kvfree(node);
+	}
+	kvfree(umem);
+}
+
 /* Caller should have device mutex if and only if locked is set */
 void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 {
@@ -549,8 +578,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 		fput(dev->log_file);
 	dev->log_file = NULL;
 	/* No one will access memory at this point */
-	kvfree(dev->memory);
-	dev->memory = NULL;
+	vhost_umem_clean(dev->umem);
+	dev->umem = NULL;
 	WARN_ON(!list_empty(&dev->work_list));
 	if (dev->worker) {
 		kthread_stop(dev->worker);
@@ -576,25 +605,25 @@ static int log_access_ok(void __user *log_base, u64 addr,
unsigned long sz)
 }
 
 /* Caller should have vq mutex and device mutex. */
-static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
+static int vq_memory_access_ok(void __user *log_base, struct vhost_umem *umem,
 			       int log_all)
 {
-	int i;
+	struct vhost_umem_node *node;
 
-	if (!mem)
+	if (!umem)
 		return 0;
 
-	for (i = 0; i < mem->nregions; ++i) {
-		struct vhost_memory_region *m = mem->regions + i;
-		unsigned long a = m->userspace_addr;
-		if (m->memory_size > ULONG_MAX)
+	list_for_each_entry(node, &umem->umem_list, link) {
+		unsigned long a = node->userspace_addr;
+
+		if (node->size > ULONG_MAX)
 			return 0;
 		else if (!access_ok(VERIFY_WRITE, (void __user *)a,
-				    m->memory_size))
+				    node->size))
 			return 0;
 		else if (log_all && !log_access_ok(log_base,
-						   m->guest_phys_addr,
-						   m->memory_size))
+						   node->start,
+						   node->size))
 			return 0;
 	}
 	return 1;
@@ -602,7 +631,7 @@ static int vq_memory_access_ok(void __user *log_base, struct
vhost_memory *mem,
 
 /* Can we switch to this memory table? */
 /* Caller should have device mutex but not vq mutex */
-static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
+static int memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
 			    int log_all)
 {
 	int i;
@@ -615,7 +644,8 @@ static int memory_access_ok(struct vhost_dev *d, struct
vhost_memory *mem,
 		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
 		/* If ring is inactive, will check when it's enabled. */
 		if (d->vqs[i]->private_data)
-			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
+			ok = vq_memory_access_ok(d->vqs[i]->log_base,
+						 umem, log);
 		else
 			ok = 1;
 		mutex_unlock(&d->vqs[i]->mutex);
@@ -642,7 +672,7 @@ static int vq_access_ok(struct vhost_virtqueue *vq, unsigned
int num,
 /* Caller should have device mutex but not vq mutex */
 int vhost_log_access_ok(struct vhost_dev *dev)
 {
-	return memory_access_ok(dev, dev->memory, 1);
+	return memory_access_ok(dev, dev->umem, 1);
 }
 EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 
@@ -653,7 +683,7 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
 {
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
-	return vq_memory_access_ok(log_base, vq->memory,
+	return vq_memory_access_ok(log_base, vq->umem,
 				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
 		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
 					sizeof *vq->used +
@@ -669,28 +699,12 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 
-static int vhost_memory_reg_sort_cmp(const void *p1, const void *p2)
-{
-	const struct vhost_memory_region *r1 = p1, *r2 = p2;
-	if (r1->guest_phys_addr < r2->guest_phys_addr)
-		return 1;
-	if (r1->guest_phys_addr > r2->guest_phys_addr)
-		return -1;
-	return 0;
-}
-
-static void *vhost_kvzalloc(unsigned long size)
-{
-	void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-
-	if (!n)
-		n = vzalloc(size);
-	return n;
-}
-
 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user
*m)
 {
-	struct vhost_memory mem, *newmem, *oldmem;
+	struct vhost_memory mem, *newmem;
+	struct vhost_memory_region *region;
+	struct vhost_umem_node *node;
+	struct vhost_umem *newumem, *oldumem;
 	unsigned long size = offsetof(struct vhost_memory, regions);
 	int i;
 
@@ -710,24 +724,52 @@ static long vhost_set_memory(struct vhost_dev *d, struct
vhost_memory __user *m)
 		kvfree(newmem);
 		return -EFAULT;
 	}
-	sort(newmem->regions, newmem->nregions, sizeof(*newmem->regions),
-		vhost_memory_reg_sort_cmp, NULL);
 
-	if (!memory_access_ok(d, newmem, 0)) {
+	newumem = vhost_kvzalloc(sizeof(*newumem));
+	if (!newumem) {
 		kvfree(newmem);
-		return -EFAULT;
+		return -ENOMEM;
+	}
+
+	newumem->umem_tree = RB_ROOT;
+	INIT_LIST_HEAD(&newumem->umem_list);
+
+	for (region = newmem->regions;
+	     region < newmem->regions + mem.nregions;
+	     region++) {
+		node = vhost_kvzalloc(sizeof(*node));
+		if (!node)
+			goto err;
+		node->start = region->guest_phys_addr;
+		node->size = region->memory_size;
+		node->last = node->start + node->size - 1;
+		node->userspace_addr = region->userspace_addr;
+		INIT_LIST_HEAD(&node->link);
+		list_add_tail(&node->link, &newumem->umem_list);
+		vhost_umem_interval_tree_insert(node, &newumem->umem_tree);
 	}
-	oldmem = d->memory;
-	d->memory = newmem;
+
+	if (!memory_access_ok(d, newumem, 0))
+		goto err;
+
+	oldumem = d->umem;
+	d->umem = newumem;
 
 	/* All memory accesses are done under some VQ mutex. */
 	for (i = 0; i < d->nvqs; ++i) {
 		mutex_lock(&d->vqs[i]->mutex);
-		d->vqs[i]->memory = newmem;
+		d->vqs[i]->umem = newumem;
 		mutex_unlock(&d->vqs[i]->mutex);
 	}
-	kvfree(oldmem);
+
+	kvfree(newmem);
+	vhost_umem_clean(oldumem);
 	return 0;
+
+err:
+	vhost_umem_clean(newumem);
+	kvfree(newmem);
+	return -EFAULT;
 }
 
 long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
@@ -1017,28 +1059,6 @@ done:
 }
 EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
 
-static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
-						     __u64 addr, __u32 len)
-{
-	const struct vhost_memory_region *reg;
-	int start = 0, end = mem->nregions;
-
-	while (start < end) {
-		int slot = start + (end - start) / 2;
-		reg = mem->regions + slot;
-		if (addr >= reg->guest_phys_addr)
-			end = slot;
-		else
-			start = slot + 1;
-	}
-
-	reg = mem->regions + start;
-	if (addr >= reg->guest_phys_addr &&
-		reg->guest_phys_addr + reg->memory_size > addr)
-		return reg;
-	return NULL;
-}
-
 /* TODO: This is really inefficient.  We need something like get_user()
  * (instruction directly accesses the data, with an exception table entry
  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
@@ -1180,29 +1200,29 @@ EXPORT_SYMBOL_GPL(vhost_init_used);
 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
 			  struct iovec iov[], int iov_size)
 {
-	const struct vhost_memory_region *reg;
-	struct vhost_memory *mem;
+	const struct vhost_umem_node *node;
+	struct vhost_umem *umem = vq->umem;
 	struct iovec *_iov;
 	u64 s = 0;
 	int ret = 0;
 
-	mem = vq->memory;
 	while ((u64)len > s) {
 		u64 size;
 		if (unlikely(ret >= iov_size)) {
 			ret = -ENOBUFS;
 			break;
 		}
-		reg = find_region(mem, addr, len);
-		if (unlikely(!reg)) {
+		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
+							addr, addr + len - 1);
+		if (node == NULL || node->start > addr) {
 			ret = -EFAULT;
 			break;
 		}
 		_iov = iov + ret;
-		size = reg->memory_size - addr + reg->guest_phys_addr;
+		size = node->size - addr + node->start;
 		_iov->iov_len = min((u64)len - s, size);
 		_iov->iov_base = (void __user *)(unsigned long)
-			(reg->userspace_addr + addr - reg->guest_phys_addr);
+			(node->userspace_addr + addr - node->start);
 		s += size;
 		addr += size;
 		++ret;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index d3f7674..5d64393 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -52,6 +52,25 @@ struct vhost_log {
 	u64 len;
 };
 
+#define START(node) ((node)->start)
+#define LAST(node) ((node)->last)
+
+struct vhost_umem_node {
+	struct rb_node rb;
+	struct list_head link;
+	__u64 start;
+	__u64 last;
+	__u64 size;
+	__u64 userspace_addr;
+	__u64 flags_padding;
+	__u64 __subtree_last;
+};
+
+struct vhost_umem {
+	struct rb_root umem_tree;
+	struct list_head umem_list;
+};
+
 /* The virtqueue structure describes a queue attached to a device. */
 struct vhost_virtqueue {
 	struct vhost_dev *dev;
@@ -100,7 +119,7 @@ struct vhost_virtqueue {
 	struct iovec *indirect;
 	struct vring_used_elem *heads;
 	/* Protected by virtqueue mutex. */
-	struct vhost_memory *memory;
+	struct vhost_umem *umem;
 	void *private_data;
 	u64 acked_features;
 	/* Log write descriptors */
@@ -117,7 +136,6 @@ struct vhost_virtqueue {
 };
 
 struct vhost_dev {
-	struct vhost_memory *memory;
 	struct mm_struct *mm;
 	struct mutex mutex;
 	struct vhost_virtqueue **vqs;
@@ -127,14 +145,15 @@ struct vhost_dev {
 	spinlock_t work_lock;
 	struct list_head work_list;
 	struct task_struct *worker;
+	struct vhost_umem *umem;
 };
 
 void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int
nvqs);
 long vhost_dev_set_owner(struct vhost_dev *dev);
 bool vhost_dev_has_owner(struct vhost_dev *dev);
 long vhost_dev_check_owner(struct vhost_dev *);
-struct vhost_memory *vhost_dev_reset_owner_prepare(void);
-void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
+struct vhost_umem *vhost_dev_reset_owner_prepare(void);
+void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_umem *);
 void vhost_dev_cleanup(struct vhost_dev *, bool locked);
 void vhost_dev_stop(struct vhost_dev *);
 long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user
*argp);
-- 
2.5.0

This patch tries to implement an device IOTLB for vhost. This could be
used with for co-operation with userspace(qemu) implementation of DMA
remapping.

The idea is simple. When vhost meets an IOTLB miss, it will request
the assistance of userspace to do the translation, this is done
through:

- Fill the translation request in a preset userspace address (This
  address is set through ioctl VHOST_SET_IOTLB_REQUEST_ENTRY).
- Notify userspace through eventfd (This eventfd was set through ioctl
  VHOST_SET_IOTLB_FD).
- device IOTLB were started and stopped through VHOST_RUN_IOTLB ioctl

When userspace finishes the translation, it will update the vhost
IOTLB through VHOST_UPDATE_IOTLB ioctl. Userspace is also in charge of
snooping the IOTLB invalidation of IOMMU IOTLB and use
VHOST_UPDATE_IOTLB to invalidate the possible entry in vhost.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/net.c        |   6 +-
 drivers/vhost/vhost.c      | 301 +++++++++++++++++++++++++++++++++++++++------
 drivers/vhost/vhost.h      |  17 ++-
 fs/eventfd.c               |   3 +-
 include/uapi/linux/vhost.h |  35 ++++++
 5 files changed, 320 insertions(+), 42 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 481db96..7cbdeed 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -334,7 +334,7 @@ static void handle_tx(struct vhost_net *net)
 		head = vhost_get_vq_desc(vq, vq->iov,
 					 ARRAY_SIZE(vq->iov),
 					 &out, &in,
-					 NULL, NULL);
+					 NULL, NULL, VHOST_ACCESS_RO);
 		/* On error, stop handling until the next kick. */
 		if (unlikely(head < 0))
 			break;
@@ -470,7 +470,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 		}
 		r = vhost_get_vq_desc(vq, vq->iov + seg,
 				      ARRAY_SIZE(vq->iov) - seg, &out,
-				      &in, log, log_num);
+				      &in, log, log_num, VHOST_ACCESS_WO);
 		if (unlikely(r < 0))
 			goto err;
 
@@ -1083,7 +1083,7 @@ static long vhost_net_ioctl(struct file *f, unsigned int
ioctl,
 		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
 		if (r == -ENOIOCTLCMD)
 			r = vhost_vring_ioctl(&n->dev, ioctl, argp);
-		else
+		else if (ioctl != VHOST_UPDATE_IOTLB)
 			vhost_net_flush(n);
 		mutex_unlock(&n->dev.mutex);
 		return r;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 32c35a9..1dd43e8 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -280,6 +280,10 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 	vq->call_ctx = NULL;
 	vq->call = NULL;
 	vq->log_ctx = NULL;
+	vq->iotlb_call = NULL;
+	vq->iotlb_call_ctx = NULL;
+	vq->iotlb_request = NULL;
+	vq->pending_request.flags.type = VHOST_IOTLB_INVALIDATE;
 	vq->umem = NULL;
 	vq->is_le = virtio_legacy_is_little_endian();
 	vhost_vq_reset_user_be(vq);
@@ -387,8 +391,10 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->log_ctx = NULL;
 	dev->log_file = NULL;
 	dev->umem = NULL;
+	dev->iotlb = NULL;
 	dev->mm = NULL;
 	spin_lock_init(&dev->work_lock);
+	spin_lock_init(&dev->iotlb_lock);
 	INIT_LIST_HEAD(&dev->work_list);
 	dev->worker = NULL;
 
@@ -537,6 +543,15 @@ void vhost_dev_stop(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_stop);
 
+static void vhost_umem_free(struct vhost_umem *umem,
+			    struct vhost_umem_node *node)
+{
+	vhost_umem_interval_tree_remove(node, &umem->umem_tree);
+	list_del(&node->link);
+	kfree(node);
+	umem->numem--;
+}
+
 static void vhost_umem_clean(struct vhost_umem *umem)
 {
 	struct vhost_umem_node *node, *tmp;
@@ -544,11 +559,9 @@ static void vhost_umem_clean(struct vhost_umem *umem)
 	if (!umem)
 		return;
 
-	list_for_each_entry_safe(node, tmp, &umem->umem_list, link) {
-		vhost_umem_interval_tree_remove(node, &umem->umem_tree);
-		list_del(&node->link);
-		kvfree(node);
-	}
+	list_for_each_entry_safe(node, tmp, &umem->umem_list, link)
+		vhost_umem_free(umem, node);
+
 	kvfree(umem);
 }
 
@@ -580,6 +593,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 	/* No one will access memory at this point */
 	vhost_umem_clean(dev->umem);
 	dev->umem = NULL;
+	vhost_umem_clean(dev->iotlb);
+	dev->iotlb = NULL;
 	WARN_ON(!list_empty(&dev->work_list));
 	if (dev->worker) {
 		kthread_stop(dev->worker);
@@ -699,11 +714,61 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 
+static int vhost_new_umem_range(struct vhost_umem *umem,
+				u64 start, u64 size, u64 end,
+				u64 userspace_addr, int perm)
+{
+	struct vhost_umem_node *tmp, *node = kmalloc(sizeof(*node), GFP_ATOMIC);
+
+	if (!node)
+		return -ENOMEM;
+
+	if (umem->numem == VHOST_IOTLB_SIZE) {
+		tmp = list_last_entry(&umem->umem_list, typeof(*tmp), link);
+		vhost_umem_free(umem, tmp);
+	}
+
+	node->start = start;
+	node->size = size;
+	node->last = end;
+	node->userspace_addr = userspace_addr;
+	node->perm = perm;
+	INIT_LIST_HEAD(&node->link);
+	list_add_tail(&node->link, &umem->umem_list);
+	vhost_umem_interval_tree_insert(node, &umem->umem_tree);
+	umem->numem++;
+
+	return 0;
+}
+
+static void vhost_del_umem_range(struct vhost_umem *umem,
+				 u64 start, u64 end)
+{
+	struct vhost_umem_node *node;
+
+	while ((node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
+							   start, end)))
+		vhost_umem_free(umem, node);
+}
+
+static struct vhost_umem *vhost_umem_alloc(void)
+{
+	struct vhost_umem *umem = vhost_kvzalloc(sizeof(*umem));
+
+	if (!umem)
+		return NULL;
+
+	umem->umem_tree = RB_ROOT;
+	umem->numem = 0;
+	INIT_LIST_HEAD(&umem->umem_list);
+
+	return umem;
+}
+
 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user
*m)
 {
 	struct vhost_memory mem, *newmem;
 	struct vhost_memory_region *region;
-	struct vhost_umem_node *node;
 	struct vhost_umem *newumem, *oldumem;
 	unsigned long size = offsetof(struct vhost_memory, regions);
 	int i;
@@ -725,28 +790,23 @@ static long vhost_set_memory(struct vhost_dev *d, struct
vhost_memory __user *m)
 		return -EFAULT;
 	}
 
-	newumem = vhost_kvzalloc(sizeof(*newumem));
+	newumem = vhost_umem_alloc();
 	if (!newumem) {
 		kvfree(newmem);
 		return -ENOMEM;
 	}
 
-	newumem->umem_tree = RB_ROOT;
-	INIT_LIST_HEAD(&newumem->umem_list);
-
 	for (region = newmem->regions;
 	     region < newmem->regions + mem.nregions;
 	     region++) {
-		node = vhost_kvzalloc(sizeof(*node));
-		if (!node)
+		if (vhost_new_umem_range(newumem,
+					 region->guest_phys_addr,
+					 region->memory_size,
+					 region->guest_phys_addr +
+					 region->memory_size - 1,
+					 region->userspace_addr,
+				         VHOST_ACCESS_RW))
 			goto err;
-		node->start = region->guest_phys_addr;
-		node->size = region->memory_size;
-		node->last = node->start + node->size - 1;
-		node->userspace_addr = region->userspace_addr;
-		INIT_LIST_HEAD(&node->link);
-		list_add_tail(&node->link, &newumem->umem_list);
-		vhost_umem_interval_tree_insert(node, &newumem->umem_tree);
 	}
 
 	if (!memory_access_ok(d, newumem, 0))
@@ -782,6 +842,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void
__user *argp)
 	struct vhost_vring_state s;
 	struct vhost_vring_file f;
 	struct vhost_vring_addr a;
+	struct vhost_vring_iotlb_entry e;
 	u32 idx;
 	long r;
 
@@ -910,6 +971,35 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void
__user *argp)
 		} else
 			filep = eventfp;
 		break;
+	case VHOST_SET_VRING_IOTLB_REQUEST:
+		r = -EFAULT;
+		if (copy_from_user(&e, argp, sizeof e))
+			break;
+		if (!access_ok(VERIFY_WRITE, e.userspace_addr,
+				sizeof(*vq->iotlb_request)))
+			break;
+		r = 0;
+		vq->iotlb_request = (struct vhost_iotlb_entry __user *)e.userspace_addr;
+		break;
+	case VHOST_SET_VRING_IOTLB_CALL:
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
+			break;
+		}
+		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
+		if (IS_ERR(eventfp)) {
+			r = PTR_ERR(eventfp);
+			break;
+		}
+		if (eventfp != vq->iotlb_call) {
+			filep = vq->iotlb_call;
+			ctx = vq->iotlb_call_ctx;
+			vq->iotlb_call = eventfp;
+			vq->iotlb_call_ctx = eventfp ?
+				eventfd_ctx_fileget(eventfp) : NULL;
+		} else
+			filep = eventfp;
+		break;
 	case VHOST_SET_VRING_CALL:
 		if (copy_from_user(&f, argp, sizeof f)) {
 			r = -EFAULT;
@@ -977,11 +1067,55 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl,
void __user *argp)
 }
 EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
 
+static int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled)
+{
+	struct vhost_umem *niotlb, *oiotlb;
+
+	if (enabled) {
+		niotlb = vhost_umem_alloc();
+		if (!niotlb)
+			return -ENOMEM;
+	} else
+		niotlb = NULL;
+
+	spin_lock(&d->iotlb_lock);
+	oiotlb = d->iotlb;
+	d->iotlb = niotlb;
+	spin_unlock(&d->iotlb_lock);
+
+	vhost_umem_clean(oiotlb);
+
+	return 0;
+}
+
+static void vhost_complete_iotlb_update(struct vhost_dev *d,
+					struct vhost_iotlb_entry *entry)
+{
+	struct vhost_iotlb_entry *req;
+	struct vhost_virtqueue *vq;
+	int i;
+
+
+	for (i = 0; i < d->nvqs; i++) {
+		vq = d->vqs[i];
+		mutex_lock(&vq->mutex);
+		req = &vq->pending_request;
+		if (entry->iova <= req->iova &&
+		    entry->iova + entry->size - 1 > req->iova &&
+		    req->flags.type == VHOST_IOTLB_MISS) {
+			*req = *entry;
+			vhost_poll_queue(&vq->poll);
+		}
+		mutex_unlock(&vq->mutex);
+	}
+}
+
 /* Caller must have device mutex */
 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user
*argp)
 {
 	struct file *eventfp, *filep = NULL;
 	struct eventfd_ctx *ctx = NULL;
+	struct vhost_iotlb_entry entry;
 	u64 p;
 	long r;
 	int i, fd;
@@ -1050,6 +1184,52 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int
ioctl, void __user *argp)
 		if (filep)
 			fput(filep);
 		break;
+	case VHOST_RUN_IOTLB:
+		/* FIXME: enable and disabled */
+		vhost_init_device_iotlb(d, true);
+		break;
+	case VHOST_UPDATE_IOTLB:
+		r = copy_from_user(&entry, argp, sizeof(entry));
+		if (r < 0) {
+			r = -EFAULT;
+			goto done;
+		}
+
+		spin_lock(&d->iotlb_lock);
+		if (!d->iotlb) {
+			spin_unlock(&d->iotlb_lock);
+			r = -EFAULT;
+			goto done;
+		}
+		switch (entry.flags.type) {
+		case VHOST_IOTLB_UPDATE:
+			if (entry.flags.valid != VHOST_IOTLB_VALID) {
+				break;
+			}
+			if (vhost_new_umem_range(d->iotlb,
+						 entry.iova,
+						 entry.size,
+						 entry.iova + entry.size - 1,
+                                                 entry.userspace_addr,
+                                                 entry.flags.perm)) {
+				r = -ENOMEM;
+				break;
+			}
+			break;
+		case VHOST_IOTLB_INVALIDATE:
+			vhost_del_umem_range(d->iotlb,
+					     entry.iova,
+					     entry.iova + entry.size - 1);
+			break;
+		default:
+			r = -EINVAL;
+		}
+		spin_unlock(&d->iotlb_lock);
+
+		if (!r && entry.flags.type != VHOST_IOTLB_INVALIDATE)
+			vhost_complete_iotlb_update(d, &entry);
+
+		break;
 	default:
 		r = -ENOIOCTLCMD;
 		break;
@@ -1197,27 +1377,69 @@ int vhost_init_used(struct vhost_virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(vhost_init_used);
 
+static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova)
+{
+	struct vhost_iotlb_entry *pending = &vq->pending_request;
+	int ret;
+
+	if (!vq->iotlb_call_ctx)
+		return -EOPNOTSUPP;
+
+	if (!vq->iotlb_request)
+		return -EOPNOTSUPP;
+
+	if (pending->flags.type == VHOST_IOTLB_MISS) {
+		return -EEXIST;
+	}
+
+	pending->iova = iova;
+	pending->flags.type = VHOST_IOTLB_MISS;
+
+	ret = __copy_to_user(vq->iotlb_request, pending,
+			     sizeof(struct vhost_iotlb_entry));
+	if (ret) {
+		goto err;
+	}
+
+	if (vq->iotlb_call_ctx)
+		eventfd_signal(vq->iotlb_call_ctx, 1);
+err:
+	return ret;
+}
+
 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
-			  struct iovec iov[], int iov_size)
+			  struct iovec iov[], int iov_size, int access)
 {
 	const struct vhost_umem_node *node;
-	struct vhost_umem *umem = vq->umem;
+	struct vhost_dev *dev = vq->dev;
+	struct vhost_umem *umem = dev->iotlb ? dev->iotlb : dev->umem;
 	struct iovec *_iov;
 	u64 s = 0;
 	int ret = 0;
 
+	spin_lock(&dev->iotlb_lock);
+
 	while ((u64)len > s) {
 		u64 size;
 		if (unlikely(ret >= iov_size)) {
 			ret = -ENOBUFS;
 			break;
 		}
+
 		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
 							addr, addr + len - 1);
 		if (node == NULL || node->start > addr) {
-			ret = -EFAULT;
+			if (umem != dev->iotlb) {
+				ret = -EFAULT;
+				break;
+			}
+			ret = -EAGAIN;
+			break;
+		} else if (!(node->perm & access)) {
+			ret = -EPERM;
 			break;
 		}
+
 		_iov = iov + ret;
 		size = node->size - addr + node->start;
 		_iov->iov_len = min((u64)len - s, size);
@@ -1228,6 +1450,10 @@ static int translate_desc(struct vhost_virtqueue *vq, u64
addr, u32 len,
 		++ret;
 	}
 
+	spin_unlock(&dev->iotlb_lock);
+
+	if (ret == -EAGAIN)
+		vhost_iotlb_miss(vq, addr);
 	return ret;
 }
 
@@ -1256,7 +1482,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
 			struct iovec iov[], unsigned int iov_size,
 			unsigned int *out_num, unsigned int *in_num,
 			struct vhost_log *log, unsigned int *log_num,
-			struct vring_desc *indirect)
+			struct vring_desc *indirect, int access)
 {
 	struct vring_desc desc;
 	unsigned int i = 0, count, found = 0;
@@ -1274,9 +1500,10 @@ static int get_indirect(struct vhost_virtqueue *vq,
 	}
 
 	ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len,
vq->indirect,
-			     UIO_MAXIOV);
+			     UIO_MAXIOV, access);
 	if (unlikely(ret < 0)) {
-		vq_err(vq, "Translation failure %d in indirect.\n", ret);
+		if (ret != -EAGAIN)
+			vq_err(vq, "Translation failure %d in indirect.\n", ret);
 		return ret;
 	}
 	iov_iter_init(&from, READ, vq->indirect, ret, len);
@@ -1316,10 +1543,11 @@ static int get_indirect(struct vhost_virtqueue *vq,
 
 		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
 				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
-				     iov_size - iov_count);
+				     iov_size - iov_count, access);
 		if (unlikely(ret < 0)) {
-			vq_err(vq, "Translation failure %d indirect idx %d\n",
-			       ret, i);
+			if (ret != -EAGAIN)
+				vq_err(vq, "Translation failure %d indirect idx %d\n",
+					ret, i);
 			return ret;
 		}
 		/* If this is an input descriptor, increment that count. */
@@ -1355,7 +1583,8 @@ static int get_indirect(struct vhost_virtqueue *vq,
 int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		      struct iovec iov[], unsigned int iov_size,
 		      unsigned int *out_num, unsigned int *in_num,
-		      struct vhost_log *log, unsigned int *log_num)
+		      struct vhost_log *log, unsigned int *log_num,
+		      int access)
 {
 	struct vring_desc desc;
 	unsigned int i, head, found = 0;
@@ -1433,10 +1662,11 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
 			ret = get_indirect(vq, iov, iov_size,
 					   out_num, in_num,
-					   log, log_num, &desc);
+					   log, log_num, &desc, access);
 			if (unlikely(ret < 0)) {
-				vq_err(vq, "Failure detected "
-				       "in indirect descriptor at idx %d\n", i);
+				if (ret != -EAGAIN)
+					vq_err(vq, "Failure detected "
+						"in indirect descriptor at idx %d\n", i);
 				return ret;
 			}
 			continue;
@@ -1444,10 +1674,11 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 
 		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
 				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
-				     iov_size - iov_count);
+				     iov_size - iov_count, access);
 		if (unlikely(ret < 0)) {
-			vq_err(vq, "Translation failure %d descriptor idx %d\n",
-			       ret, i);
+			if (ret != -EAGAIN)
+				vq_err(vq, "Translation failure %d descriptor idx %d\n",
+					ret, i);
 			return ret;
 		}
 		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 5d64393..4365104 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -62,13 +62,15 @@ struct vhost_umem_node {
 	__u64 last;
 	__u64 size;
 	__u64 userspace_addr;
-	__u64 flags_padding;
+	__u32 perm;
+	__u32 flags_padding;
 	__u64 __subtree_last;
 };
 
 struct vhost_umem {
 	struct rb_root umem_tree;
 	struct list_head umem_list;
+	int numem;
 };
 
 /* The virtqueue structure describes a queue attached to a device. */
@@ -84,9 +86,13 @@ struct vhost_virtqueue {
 	struct file *kick;
 	struct file *call;
 	struct file *error;
+	struct file *iotlb_call;
 	struct eventfd_ctx *call_ctx;
 	struct eventfd_ctx *error_ctx;
 	struct eventfd_ctx *log_ctx;
+	struct eventfd_ctx *iotlb_call_ctx;
+	struct vhost_iotlb_entry __user *iotlb_request;
+	struct vhost_iotlb_entry pending_request;
 
 	struct vhost_poll poll;
 
@@ -135,6 +141,8 @@ struct vhost_virtqueue {
 #endif
 };
 
+#define VHOST_IOTLB_SIZE 2048
+
 struct vhost_dev {
 	struct mm_struct *mm;
 	struct mutex mutex;
@@ -146,6 +154,8 @@ struct vhost_dev {
 	struct list_head work_list;
 	struct task_struct *worker;
 	struct vhost_umem *umem;
+	struct vhost_umem *iotlb;
+	spinlock_t iotlb_lock;
 };
 
 void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int
nvqs);
@@ -164,7 +174,8 @@ int vhost_log_access_ok(struct vhost_dev *);
 int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct iovec iov[], unsigned int iov_count,
 		      unsigned int *out_num, unsigned int *in_num,
-		      struct vhost_log *log, unsigned int *log_num);
+		      struct vhost_log *log, unsigned int *log_num,
+		      int access);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_init_used(struct vhost_virtqueue *);
@@ -183,7 +194,7 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct
vhost_log *log,
 		    unsigned int log_num, u64 len);
 
 #define vq_err(vq, fmt, ...) do {                                  \
-		pr_debug(pr_fmt(fmt), ##__VA_ARGS__);       \
+		printk(pr_fmt(fmt), ##__VA_ARGS__);       \
 		if ((vq)->error_ctx)                               \
 				eventfd_signal((vq)->error_ctx, 1);\
 	} while (0)
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 8d0c0df..5c0a22f 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -59,8 +59,9 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
 	if (ULLONG_MAX - ctx->count < n)
 		n = ULLONG_MAX - ctx->count;
 	ctx->count += n;
-	if (waitqueue_active(&ctx->wqh))
+	if (waitqueue_active(&ctx->wqh)) {
 		wake_up_locked_poll(&ctx->wqh, POLLIN);
+	}
 	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
 
 	return n;
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index ab373191..5c35ab4 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -47,6 +47,32 @@ struct vhost_vring_addr {
 	__u64 log_guest_addr;
 };
 
+struct vhost_iotlb_entry {
+	__u64 iova;
+	__u64 size;
+	__u64 userspace_addr;
+	struct {
+#define VHOST_ACCESS_RO      0x1
+#define VHOST_ACCESS_WO      0x2
+#define VHOST_ACCESS_RW      0x3
+		__u8  perm;
+#define VHOST_IOTLB_MISS           1
+#define VHOST_IOTLB_UPDATE         2
+#define VHOST_IOTLB_INVALIDATE     3
+		__u8  type;
+#define VHOST_IOTLB_INVALID        0x1
+#define VHOST_IOTLB_VALID          0x2
+		__u8  valid;
+		__u8  u8_padding;
+		__u32 padding;
+	} flags;
+};
+
+struct vhost_vring_iotlb_entry {
+	unsigned int index;
+	__u64 userspace_addr;
+};
+
 struct vhost_memory_region {
 	__u64 guest_phys_addr;
 	__u64 memory_size; /* bytes */
@@ -127,6 +153,15 @@ struct vhost_memory {
 /* Set eventfd to signal an error */
 #define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)
 
+/* IOTLB */
+/* Specify an eventfd file descriptor to signle on IOTLB miss */
+#define VHOST_SET_VRING_IOTLB_CALL _IOW(VHOST_VIRTIO, 0x23, struct      \
+                                        vhost_vring_file)
+#define VHOST_SET_VRING_IOTLB_REQUEST _IOW(VHOST_VIRTIO, 0x25, struct   \
+                                           vhost_vring_iotlb_entry)
+#define VHOST_UPDATE_IOTLB _IOW(VHOST_VIRTIO, 0x24, struct vhost_iotlb_entry)
+#define VHOST_RUN_IOTLB _IOW(VHOST_VIRTIO, 0x26, int)
+
 /* VHOST_NET specific defines */
 
 /* Attach virtio net ring to a raw socket, or tap device.
-- 
2.5.0

On Fri, Mar 25, 2016 at 10:34:33AM +0800, Jason Wang
wrote:
> Current pre-sorted memory region array has some limitations for future
> device IOTLB conversion:
> 
> 1) need extra work for adding and removing a single region, and it's
>    expected to be slow because of sorting or memory re-allocation.
> 2) need extra work of removing a large range which may intersect
>    several regions with different size.
> 3) need trick for a replacement policy like LRU
> 
> To overcome the above shortcomings, this patch convert it to interval
> tree which can easily address the above issue with almost no extra
> work.
> 
> The patch could be used for:
> 
> - Extend the current API and only let the userspace to send diffs of
>   memory table.
> - Simplify Device IOTLB implementation.
Does this affect performance at all?
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  drivers/vhost/net.c   |   8 +--
>  drivers/vhost/vhost.c | 182
++++++++++++++++++++++++++++----------------------
>  drivers/vhost/vhost.h |  27 ++++++--
>  3 files changed, 128 insertions(+), 89 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 9eda69e..481db96 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -968,20 +968,20 @@ static long vhost_net_reset_owner(struct vhost_net
*n)
>  	struct socket *tx_sock = NULL;
>  	struct socket *rx_sock = NULL;
>  	long err;
> -	struct vhost_memory *memory;
> +	struct vhost_umem *umem;
>  
>  	mutex_lock(&n->dev.mutex);
>  	err = vhost_dev_check_owner(&n->dev);
>  	if (err)
>  		goto done;
> -	memory = vhost_dev_reset_owner_prepare();
> -	if (!memory) {
> +	umem = vhost_dev_reset_owner_prepare();
> +	if (!umem) {
>  		err = -ENOMEM;
>  		goto done;
>  	}
>  	vhost_net_stop(n, &tx_sock, &rx_sock);
>  	vhost_net_flush(n);
> -	vhost_dev_reset_owner(&n->dev, memory);
> +	vhost_dev_reset_owner(&n->dev, umem);
>  	vhost_net_vq_reset(n);
>  done:
>  	mutex_unlock(&n->dev.mutex);
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index ad2146a..32c35a9 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -27,6 +27,7 @@
>  #include <linux/cgroup.h>
>  #include <linux/module.h>
>  #include <linux/sort.h>
> +#include <linux/interval_tree_generic.h>
>  
>  #include "vhost.h"
>  
> @@ -42,6 +43,10 @@ enum {
>  #define vhost_used_event(vq) ((__virtio16 __user
*)&vq->avail->ring[vq->num])
>  #define vhost_avail_event(vq) ((__virtio16 __user
*)&vq->used->ring[vq->num])
>  
> +INTERVAL_TREE_DEFINE(struct vhost_umem_node,
> +		     rb, __u64, __subtree_last,
> +		     START, LAST, , vhost_umem_interval_tree);
> +
>  #ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
>  static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
>  {
> @@ -275,7 +280,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>  	vq->call_ctx = NULL;
>  	vq->call = NULL;
>  	vq->log_ctx = NULL;
> -	vq->memory = NULL;
> +	vq->umem = NULL;
>  	vq->is_le = virtio_legacy_is_little_endian();
>  	vhost_vq_reset_user_be(vq);
>  }
> @@ -381,7 +386,7 @@ void vhost_dev_init(struct vhost_dev *dev,
>  	mutex_init(&dev->mutex);
>  	dev->log_ctx = NULL;
>  	dev->log_file = NULL;
> -	dev->memory = NULL;
> +	dev->umem = NULL;
>  	dev->mm = NULL;
>  	spin_lock_init(&dev->work_lock);
>  	INIT_LIST_HEAD(&dev->work_list);
> @@ -486,27 +491,36 @@ err_mm:
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
>  
> -struct vhost_memory *vhost_dev_reset_owner_prepare(void)
> +static void *vhost_kvzalloc(unsigned long size)
> +{
> +	void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> +
> +	if (!n)
> +		n = vzalloc(size);
> +	return n;
> +}
> +
> +struct vhost_umem *vhost_dev_reset_owner_prepare(void)
>  {
> -	return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
> +	return vhost_kvzalloc(sizeof(struct vhost_umem));
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
>  
>  /* Caller should have device mutex */
> -void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory
*memory)
> +void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_umem *umem)
>  {
>  	int i;
>  
>  	vhost_dev_cleanup(dev, true);
>  
>  	/* Restore memory to default empty mapping. */
> -	memory->nregions = 0;
> -	dev->memory = memory;
> +	INIT_LIST_HEAD(&umem->umem_list);
> +	dev->umem = umem;
>  	/* We don't need VQ locks below since vhost_dev_cleanup makes sure
>  	 * VQs aren't running.
>  	 */
>  	for (i = 0; i < dev->nvqs; ++i)
> -		dev->vqs[i]->memory = memory;
> +		dev->vqs[i]->umem = umem;
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
>  
> @@ -523,6 +537,21 @@ void vhost_dev_stop(struct vhost_dev *dev)
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_stop);
>  
> +static void vhost_umem_clean(struct vhost_umem *umem)
> +{
> +	struct vhost_umem_node *node, *tmp;
> +
> +	if (!umem)
> +		return;
> +
> +	list_for_each_entry_safe(node, tmp, &umem->umem_list, link) {
> +		vhost_umem_interval_tree_remove(node, &umem->umem_tree);
> +		list_del(&node->link);
> +		kvfree(node);
> +	}
> +	kvfree(umem);
> +}
> +
>  /* Caller should have device mutex if and only if locked is set */
>  void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
>  {
> @@ -549,8 +578,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool
locked)
>  		fput(dev->log_file);
>  	dev->log_file = NULL;
>  	/* No one will access memory at this point */
> -	kvfree(dev->memory);
> -	dev->memory = NULL;
> +	vhost_umem_clean(dev->umem);
> +	dev->umem = NULL;
>  	WARN_ON(!list_empty(&dev->work_list));
>  	if (dev->worker) {
>  		kthread_stop(dev->worker);
> @@ -576,25 +605,25 @@ static int log_access_ok(void __user *log_base, u64
addr, unsigned long sz)
>  }
>  
>  /* Caller should have vq mutex and device mutex. */
> -static int vq_memory_access_ok(void __user *log_base, struct vhost_memory
*mem,
> +static int vq_memory_access_ok(void __user *log_base, struct vhost_umem
*umem,
>  			       int log_all)
>  {
> -	int i;
> +	struct vhost_umem_node *node;
>  
> -	if (!mem)
> +	if (!umem)
>  		return 0;
>  
> -	for (i = 0; i < mem->nregions; ++i) {
> -		struct vhost_memory_region *m = mem->regions + i;
> -		unsigned long a = m->userspace_addr;
> -		if (m->memory_size > ULONG_MAX)
> +	list_for_each_entry(node, &umem->umem_list, link) {
> +		unsigned long a = node->userspace_addr;
> +
> +		if (node->size > ULONG_MAX)
>  			return 0;
>  		else if (!access_ok(VERIFY_WRITE, (void __user *)a,
> -				    m->memory_size))
> +				    node->size))
>  			return 0;
>  		else if (log_all && !log_access_ok(log_base,
> -						   m->guest_phys_addr,
> -						   m->memory_size))
> +						   node->start,
> +						   node->size))
>  			return 0;
>  	}
>  	return 1;
> @@ -602,7 +631,7 @@ static int vq_memory_access_ok(void __user *log_base,
struct vhost_memory *mem,
>  
>  /* Can we switch to this memory table? */
>  /* Caller should have device mutex but not vq mutex */
> -static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
> +static int memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
>  			    int log_all)
>  {
>  	int i;
> @@ -615,7 +644,8 @@ static int memory_access_ok(struct vhost_dev *d, struct
vhost_memory *mem,
>  		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
>  		/* If ring is inactive, will check when it's enabled. */
>  		if (d->vqs[i]->private_data)
> -			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
> +			ok = vq_memory_access_ok(d->vqs[i]->log_base,
> +						 umem, log);
>  		else
>  			ok = 1;
>  		mutex_unlock(&d->vqs[i]->mutex);
> @@ -642,7 +672,7 @@ static int vq_access_ok(struct vhost_virtqueue *vq,
unsigned int num,
>  /* Caller should have device mutex but not vq mutex */
>  int vhost_log_access_ok(struct vhost_dev *dev)
>  {
> -	return memory_access_ok(dev, dev->memory, 1);
> +	return memory_access_ok(dev, dev->umem, 1);
>  }
>  EXPORT_SYMBOL_GPL(vhost_log_access_ok);
>  
> @@ -653,7 +683,7 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
>  {
>  	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
>  
> -	return vq_memory_access_ok(log_base, vq->memory,
> +	return vq_memory_access_ok(log_base, vq->umem,
>  				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
>  		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
>  					sizeof *vq->used +
> @@ -669,28 +699,12 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
>  }
>  EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
>  
> -static int vhost_memory_reg_sort_cmp(const void *p1, const void *p2)
> -{
> -	const struct vhost_memory_region *r1 = p1, *r2 = p2;
> -	if (r1->guest_phys_addr < r2->guest_phys_addr)
> -		return 1;
> -	if (r1->guest_phys_addr > r2->guest_phys_addr)
> -		return -1;
> -	return 0;
> -}
> -
> -static void *vhost_kvzalloc(unsigned long size)
> -{
> -	void *n = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> -
> -	if (!n)
> -		n = vzalloc(size);
> -	return n;
> -}
> -
>  static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory
__user *m)
>  {
> -	struct vhost_memory mem, *newmem, *oldmem;
> +	struct vhost_memory mem, *newmem;
> +	struct vhost_memory_region *region;
> +	struct vhost_umem_node *node;
> +	struct vhost_umem *newumem, *oldumem;
>  	unsigned long size = offsetof(struct vhost_memory, regions);
>  	int i;
>  
> @@ -710,24 +724,52 @@ static long vhost_set_memory(struct vhost_dev *d,
struct vhost_memory __user *m)
>  		kvfree(newmem);
>  		return -EFAULT;
>  	}
> -	sort(newmem->regions, newmem->nregions,
sizeof(*newmem->regions),
> -		vhost_memory_reg_sort_cmp, NULL);
>  
> -	if (!memory_access_ok(d, newmem, 0)) {
> +	newumem = vhost_kvzalloc(sizeof(*newumem));
> +	if (!newumem) {
>  		kvfree(newmem);
> -		return -EFAULT;
> +		return -ENOMEM;
> +	}
> +
> +	newumem->umem_tree = RB_ROOT;
> +	INIT_LIST_HEAD(&newumem->umem_list);
> +
> +	for (region = newmem->regions;
> +	     region < newmem->regions + mem.nregions;
> +	     region++) {
> +		node = vhost_kvzalloc(sizeof(*node));
> +		if (!node)
> +			goto err;
> +		node->start = region->guest_phys_addr;
> +		node->size = region->memory_size;
> +		node->last = node->start + node->size - 1;
> +		node->userspace_addr = region->userspace_addr;
> +		INIT_LIST_HEAD(&node->link);
> +		list_add_tail(&node->link, &newumem->umem_list);
> +		vhost_umem_interval_tree_insert(node, &newumem->umem_tree);
>  	}
> -	oldmem = d->memory;
> -	d->memory = newmem;
> +
> +	if (!memory_access_ok(d, newumem, 0))
> +		goto err;
> +
> +	oldumem = d->umem;
> +	d->umem = newumem;
>  
>  	/* All memory accesses are done under some VQ mutex. */
>  	for (i = 0; i < d->nvqs; ++i) {
>  		mutex_lock(&d->vqs[i]->mutex);
> -		d->vqs[i]->memory = newmem;
> +		d->vqs[i]->umem = newumem;
>  		mutex_unlock(&d->vqs[i]->mutex);
>  	}
> -	kvfree(oldmem);
> +
> +	kvfree(newmem);
> +	vhost_umem_clean(oldumem);
>  	return 0;
> +
> +err:
> +	vhost_umem_clean(newumem);
> +	kvfree(newmem);
> +	return -EFAULT;
>  }
>  
>  long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
> @@ -1017,28 +1059,6 @@ done:
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
>  
> -static const struct vhost_memory_region *find_region(struct vhost_memory
*mem,
> -						     __u64 addr, __u32 len)
> -{
> -	const struct vhost_memory_region *reg;
> -	int start = 0, end = mem->nregions;
> -
> -	while (start < end) {
> -		int slot = start + (end - start) / 2;
> -		reg = mem->regions + slot;
> -		if (addr >= reg->guest_phys_addr)
> -			end = slot;
> -		else
> -			start = slot + 1;
> -	}
> -
> -	reg = mem->regions + start;
> -	if (addr >= reg->guest_phys_addr &&
> -		reg->guest_phys_addr + reg->memory_size > addr)
> -		return reg;
> -	return NULL;
> -}
> -
>  /* TODO: This is really inefficient.  We need something like get_user()
>   * (instruction directly accesses the data, with an exception table entry
>   * returning -EFAULT). See Documentation/x86/exception-tables.txt.
> @@ -1180,29 +1200,29 @@ EXPORT_SYMBOL_GPL(vhost_init_used);
>  static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
>  			  struct iovec iov[], int iov_size)
>  {
> -	const struct vhost_memory_region *reg;
> -	struct vhost_memory *mem;
> +	const struct vhost_umem_node *node;
> +	struct vhost_umem *umem = vq->umem;
>  	struct iovec *_iov;
>  	u64 s = 0;
>  	int ret = 0;
>  
> -	mem = vq->memory;
>  	while ((u64)len > s) {
>  		u64 size;
>  		if (unlikely(ret >= iov_size)) {
>  			ret = -ENOBUFS;
>  			break;
>  		}
> -		reg = find_region(mem, addr, len);
> -		if (unlikely(!reg)) {
> +		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
> +							addr, addr + len - 1);
> +		if (node == NULL || node->start > addr) {
>  			ret = -EFAULT;
>  			break;
>  		}
>  		_iov = iov + ret;
> -		size = reg->memory_size - addr + reg->guest_phys_addr;
> +		size = node->size - addr + node->start;
>  		_iov->iov_len = min((u64)len - s, size);
>  		_iov->iov_base = (void __user *)(unsigned long)
> -			(reg->userspace_addr + addr - reg->guest_phys_addr);
> +			(node->userspace_addr + addr - node->start);
>  		s += size;
>  		addr += size;
>  		++ret;
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index d3f7674..5d64393 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -52,6 +52,25 @@ struct vhost_log {
>  	u64 len;
>  };
>  
> +#define START(node) ((node)->start)
> +#define LAST(node) ((node)->last)
> +
> +struct vhost_umem_node {
> +	struct rb_node rb;
> +	struct list_head link;
> +	__u64 start;
> +	__u64 last;
> +	__u64 size;
> +	__u64 userspace_addr;
> +	__u64 flags_padding;
> +	__u64 __subtree_last;
> +};
> +
> +struct vhost_umem {
> +	struct rb_root umem_tree;
> +	struct list_head umem_list;
> +};
> +
>  /* The virtqueue structure describes a queue attached to a device. */
>  struct vhost_virtqueue {
>  	struct vhost_dev *dev;
> @@ -100,7 +119,7 @@ struct vhost_virtqueue {
>  	struct iovec *indirect;
>  	struct vring_used_elem *heads;
>  	/* Protected by virtqueue mutex. */
> -	struct vhost_memory *memory;
> +	struct vhost_umem *umem;
>  	void *private_data;
>  	u64 acked_features;
>  	/* Log write descriptors */
> @@ -117,7 +136,6 @@ struct vhost_virtqueue {
>  };
>  
>  struct vhost_dev {
> -	struct vhost_memory *memory;
>  	struct mm_struct *mm;
>  	struct mutex mutex;
>  	struct vhost_virtqueue **vqs;
> @@ -127,14 +145,15 @@ struct vhost_dev {
>  	spinlock_t work_lock;
>  	struct list_head work_list;
>  	struct task_struct *worker;
> +	struct vhost_umem *umem;
>  };
>  
>  void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int
nvqs);
>  long vhost_dev_set_owner(struct vhost_dev *dev);
>  bool vhost_dev_has_owner(struct vhost_dev *dev);
>  long vhost_dev_check_owner(struct vhost_dev *);
> -struct vhost_memory *vhost_dev_reset_owner_prepare(void);
> -void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
> +struct vhost_umem *vhost_dev_reset_owner_prepare(void);
> +void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_umem *);
>  void vhost_dev_cleanup(struct vhost_dev *, bool locked);
>  void vhost_dev_stop(struct vhost_dev *);
>  long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user
*argp);
> -- 
> 2.5.0

On Fri, Mar 25, 2016 at 10:34:34AM +0800, Jason Wang
wrote:
> This patch tries to implement an device IOTLB for vhost. This could be
> used with for co-operation with userspace(qemu) implementation of DMA
> remapping.
> 
> The idea is simple. When vhost meets an IOTLB miss, it will request
> the assistance of userspace to do the translation, this is done
> through:
> 
> - Fill the translation request in a preset userspace address (This
>   address is set through ioctl VHOST_SET_IOTLB_REQUEST_ENTRY).
> - Notify userspace through eventfd (This eventfd was set through ioctl
>   VHOST_SET_IOTLB_FD).
Why use an eventfd for this? We use them for interrupts because
that happens to be what kvm wants, but here - why don't we
just add a generic support for reading out events
on the vhost fd itself?
> - device IOTLB were started and stopped through VHOST_RUN_IOTLB ioctl
> 
> When userspace finishes the translation, it will update the vhost
> IOTLB through VHOST_UPDATE_IOTLB ioctl. Userspace is also in charge of
> snooping the IOTLB invalidation of IOMMU IOTLB and use
> VHOST_UPDATE_IOTLB to invalidate the possible entry in vhost.
There's one problem here, and that is that VQs still do not undergo
translation.  In theory VQ could be mapped in such a way
that it's not contigious in userspace memory.

> Signed-off-by: Jason Wang <jasowang at redhat.com>
What limits amount of entries that kernel keeps around?
Do we want at least a mod parameter for this?

> ---
>  drivers/vhost/net.c        |   6 +-
>  drivers/vhost/vhost.c      | 301
+++++++++++++++++++++++++++++++++++++++------
>  drivers/vhost/vhost.h      |  17 ++-
>  fs/eventfd.c               |   3 +-
>  include/uapi/linux/vhost.h |  35 ++++++
>  5 files changed, 320 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 481db96..7cbdeed 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -334,7 +334,7 @@ static void handle_tx(struct vhost_net *net)
>  		head = vhost_get_vq_desc(vq, vq->iov,
>  					 ARRAY_SIZE(vq->iov),
>  					 &out, &in,
> -					 NULL, NULL);
> +					 NULL, NULL, VHOST_ACCESS_RO);
>  		/* On error, stop handling until the next kick. */
>  		if (unlikely(head < 0))
>  			break;
> @@ -470,7 +470,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
>  		}
>  		r = vhost_get_vq_desc(vq, vq->iov + seg,
>  				      ARRAY_SIZE(vq->iov) - seg, &out,
> -				      &in, log, log_num);
> +				      &in, log, log_num, VHOST_ACCESS_WO);
>  		if (unlikely(r < 0))
>  			goto err;
>  
> @@ -1083,7 +1083,7 @@ static long vhost_net_ioctl(struct file *f, unsigned
int ioctl,
>  		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
>  		if (r == -ENOIOCTLCMD)
>  			r = vhost_vring_ioctl(&n->dev, ioctl, argp);
> -		else
> +		else if (ioctl != VHOST_UPDATE_IOTLB)
>  			vhost_net_flush(n);
>  		mutex_unlock(&n->dev.mutex);
>  		return r;
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 32c35a9..1dd43e8 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -280,6 +280,10 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>  	vq->call_ctx = NULL;
>  	vq->call = NULL;
>  	vq->log_ctx = NULL;
> +	vq->iotlb_call = NULL;
> +	vq->iotlb_call_ctx = NULL;
> +	vq->iotlb_request = NULL;
> +	vq->pending_request.flags.type = VHOST_IOTLB_INVALIDATE;
>  	vq->umem = NULL;
>  	vq->is_le = virtio_legacy_is_little_endian();
>  	vhost_vq_reset_user_be(vq);
> @@ -387,8 +391,10 @@ void vhost_dev_init(struct vhost_dev *dev,
>  	dev->log_ctx = NULL;
>  	dev->log_file = NULL;
>  	dev->umem = NULL;
> +	dev->iotlb = NULL;
>  	dev->mm = NULL;
>  	spin_lock_init(&dev->work_lock);
> +	spin_lock_init(&dev->iotlb_lock);
>  	INIT_LIST_HEAD(&dev->work_list);
>  	dev->worker = NULL;
>  
> @@ -537,6 +543,15 @@ void vhost_dev_stop(struct vhost_dev *dev)
>  }
>  EXPORT_SYMBOL_GPL(vhost_dev_stop);
>  
> +static void vhost_umem_free(struct vhost_umem *umem,
> +			    struct vhost_umem_node *node)
> +{
> +	vhost_umem_interval_tree_remove(node, &umem->umem_tree);
> +	list_del(&node->link);
> +	kfree(node);
> +	umem->numem--;
> +}
> +
>  static void vhost_umem_clean(struct vhost_umem *umem)
>  {
>  	struct vhost_umem_node *node, *tmp;
> @@ -544,11 +559,9 @@ static void vhost_umem_clean(struct vhost_umem *umem)
>  	if (!umem)
>  		return;
>  
> -	list_for_each_entry_safe(node, tmp, &umem->umem_list, link) {
> -		vhost_umem_interval_tree_remove(node, &umem->umem_tree);
> -		list_del(&node->link);
> -		kvfree(node);
> -	}
> +	list_for_each_entry_safe(node, tmp, &umem->umem_list, link)
> +		vhost_umem_free(umem, node);
> +
>  	kvfree(umem);
>  }
>  
> @@ -580,6 +593,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool
locked)
>  	/* No one will access memory at this point */
>  	vhost_umem_clean(dev->umem);
>  	dev->umem = NULL;
> +	vhost_umem_clean(dev->iotlb);
> +	dev->iotlb = NULL;
>  	WARN_ON(!list_empty(&dev->work_list));
>  	if (dev->worker) {
>  		kthread_stop(dev->worker);
> @@ -699,11 +714,61 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
>  }
>  EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
>  
> +static int vhost_new_umem_range(struct vhost_umem *umem,
> +				u64 start, u64 size, u64 end,
> +				u64 userspace_addr, int perm)
> +{
> +	struct vhost_umem_node *tmp, *node = kmalloc(sizeof(*node), GFP_ATOMIC);
> +
> +	if (!node)
> +		return -ENOMEM;
> +
> +	if (umem->numem == VHOST_IOTLB_SIZE) {
> +		tmp = list_last_entry(&umem->umem_list, typeof(*tmp), link);
> +		vhost_umem_free(umem, tmp);
> +	}
> +
> +	node->start = start;
> +	node->size = size;
> +	node->last = end;
> +	node->userspace_addr = userspace_addr;
> +	node->perm = perm;
> +	INIT_LIST_HEAD(&node->link);
> +	list_add_tail(&node->link, &umem->umem_list);
> +	vhost_umem_interval_tree_insert(node, &umem->umem_tree);
> +	umem->numem++;
> +
> +	return 0;
> +}
> +
> +static void vhost_del_umem_range(struct vhost_umem *umem,
> +				 u64 start, u64 end)
> +{
> +	struct vhost_umem_node *node;
> +
> +	while ((node =
vhost_umem_interval_tree_iter_first(&umem->umem_tree,
> +							   start, end)))
> +		vhost_umem_free(umem, node);
> +}
> +
> +static struct vhost_umem *vhost_umem_alloc(void)
> +{
> +	struct vhost_umem *umem = vhost_kvzalloc(sizeof(*umem));
> +
> +	if (!umem)
> +		return NULL;
> +
> +	umem->umem_tree = RB_ROOT;
> +	umem->numem = 0;
> +	INIT_LIST_HEAD(&umem->umem_list);
> +
> +	return umem;
> +}
> +
>  static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory
__user *m)
>  {
>  	struct vhost_memory mem, *newmem;
>  	struct vhost_memory_region *region;
> -	struct vhost_umem_node *node;
>  	struct vhost_umem *newumem, *oldumem;
>  	unsigned long size = offsetof(struct vhost_memory, regions);
>  	int i;
> @@ -725,28 +790,23 @@ static long vhost_set_memory(struct vhost_dev *d,
struct vhost_memory __user *m)
>  		return -EFAULT;
>  	}
>  
> -	newumem = vhost_kvzalloc(sizeof(*newumem));
> +	newumem = vhost_umem_alloc();
>  	if (!newumem) {
>  		kvfree(newmem);
>  		return -ENOMEM;
>  	}
>  
> -	newumem->umem_tree = RB_ROOT;
> -	INIT_LIST_HEAD(&newumem->umem_list);
> -
>  	for (region = newmem->regions;
>  	     region < newmem->regions + mem.nregions;
>  	     region++) {
> -		node = vhost_kvzalloc(sizeof(*node));
> -		if (!node)
> +		if (vhost_new_umem_range(newumem,
> +					 region->guest_phys_addr,
> +					 region->memory_size,
> +					 region->guest_phys_addr +
> +					 region->memory_size - 1,
> +					 region->userspace_addr,
> +				         VHOST_ACCESS_RW))
>  			goto err;
> -		node->start = region->guest_phys_addr;
> -		node->size = region->memory_size;
> -		node->last = node->start + node->size - 1;
> -		node->userspace_addr = region->userspace_addr;
> -		INIT_LIST_HEAD(&node->link);
> -		list_add_tail(&node->link, &newumem->umem_list);
> -		vhost_umem_interval_tree_insert(node, &newumem->umem_tree);
>  	}
>  
>  	if (!memory_access_ok(d, newumem, 0))
> @@ -782,6 +842,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl,
void __user *argp)
>  	struct vhost_vring_state s;
>  	struct vhost_vring_file f;
>  	struct vhost_vring_addr a;
> +	struct vhost_vring_iotlb_entry e;
>  	u32 idx;
>  	long r;
>  
> @@ -910,6 +971,35 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl,
void __user *argp)
>  		} else
>  			filep = eventfp;
>  		break;
> +	case VHOST_SET_VRING_IOTLB_REQUEST:
> +		r = -EFAULT;
> +		if (copy_from_user(&e, argp, sizeof e))
> +			break;
> +		if (!access_ok(VERIFY_WRITE, e.userspace_addr,
> +				sizeof(*vq->iotlb_request)))
> +			break;
> +		r = 0;
> +		vq->iotlb_request = (struct vhost_iotlb_entry __user
*)e.userspace_addr;
> +		break;
> +	case VHOST_SET_VRING_IOTLB_CALL:
> +		if (copy_from_user(&f, argp, sizeof f)) {
> +			r = -EFAULT;
> +			break;
> +		}
> +		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
> +		if (IS_ERR(eventfp)) {
> +			r = PTR_ERR(eventfp);
> +			break;
> +		}
> +		if (eventfp != vq->iotlb_call) {
> +			filep = vq->iotlb_call;
> +			ctx = vq->iotlb_call_ctx;
> +			vq->iotlb_call = eventfp;
> +			vq->iotlb_call_ctx = eventfp ?
> +				eventfd_ctx_fileget(eventfp) : NULL;
> +		} else
> +			filep = eventfp;
> +		break;
>  	case VHOST_SET_VRING_CALL:
>  		if (copy_from_user(&f, argp, sizeof f)) {
>  			r = -EFAULT;
> @@ -977,11 +1067,55 @@ long vhost_vring_ioctl(struct vhost_dev *d, int
ioctl, void __user *argp)
>  }
>  EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
>  
> +static int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled)
> +{
> +	struct vhost_umem *niotlb, *oiotlb;
> +
> +	if (enabled) {
> +		niotlb = vhost_umem_alloc();
> +		if (!niotlb)
> +			return -ENOMEM;
> +	} else
> +		niotlb = NULL;
> +
> +	spin_lock(&d->iotlb_lock);
> +	oiotlb = d->iotlb;
> +	d->iotlb = niotlb;
> +	spin_unlock(&d->iotlb_lock);
> +
> +	vhost_umem_clean(oiotlb);
> +
> +	return 0;
> +}
> +
> +static void vhost_complete_iotlb_update(struct vhost_dev *d,
> +					struct vhost_iotlb_entry *entry)
> +{
> +	struct vhost_iotlb_entry *req;
> +	struct vhost_virtqueue *vq;
> +	int i;
> +
> +
> +	for (i = 0; i < d->nvqs; i++) {
> +		vq = d->vqs[i];
> +		mutex_lock(&vq->mutex);
> +		req = &vq->pending_request;
> +		if (entry->iova <= req->iova &&
> +		    entry->iova + entry->size - 1 > req->iova &&
> +		    req->flags.type == VHOST_IOTLB_MISS) {
> +			*req = *entry;
> +			vhost_poll_queue(&vq->poll);
> +		}
> +		mutex_unlock(&vq->mutex);
> +	}
> +}
> +
>  /* Caller must have device mutex */
>  long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user
*argp)
>  {
>  	struct file *eventfp, *filep = NULL;
>  	struct eventfd_ctx *ctx = NULL;
> +	struct vhost_iotlb_entry entry;
>  	u64 p;
>  	long r;
>  	int i, fd;
> @@ -1050,6 +1184,52 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned
int ioctl, void __user *argp)
>  		if (filep)
>  			fput(filep);
>  		break;
> +	case VHOST_RUN_IOTLB:
> +		/* FIXME: enable and disabled */
> +		vhost_init_device_iotlb(d, true);
> +		break;
> +	case VHOST_UPDATE_IOTLB:
> +		r = copy_from_user(&entry, argp, sizeof(entry));
> +		if (r < 0) {
> +			r = -EFAULT;
> +			goto done;
> +		}
> +
> +		spin_lock(&d->iotlb_lock);
> +		if (!d->iotlb) {
> +			spin_unlock(&d->iotlb_lock);
> +			r = -EFAULT;
> +			goto done;
> +		}
> +		switch (entry.flags.type) {
> +		case VHOST_IOTLB_UPDATE:
> +			if (entry.flags.valid != VHOST_IOTLB_VALID) {
> +				break;
> +			}
> +			if (vhost_new_umem_range(d->iotlb,
> +						 entry.iova,
> +						 entry.size,
> +						 entry.iova + entry.size - 1,
> +                                                 entry.userspace_addr,
> +                                                 entry.flags.perm)) {
> +				r = -ENOMEM;
> +				break;
> +			}
> +			break;
> +		case VHOST_IOTLB_INVALIDATE:
> +			vhost_del_umem_range(d->iotlb,
> +					     entry.iova,
> +					     entry.iova + entry.size - 1);
> +			break;
> +		default:
> +			r = -EINVAL;
> +		}
> +		spin_unlock(&d->iotlb_lock);
> +
> +		if (!r && entry.flags.type != VHOST_IOTLB_INVALIDATE)
> +			vhost_complete_iotlb_update(d, &entry);
> +
> +		break;
>  	default:
>  		r = -ENOIOCTLCMD;
>  		break;
> @@ -1197,27 +1377,69 @@ int vhost_init_used(struct vhost_virtqueue *vq)
>  }
>  EXPORT_SYMBOL_GPL(vhost_init_used);
>  
> +static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova)
> +{
> +	struct vhost_iotlb_entry *pending = &vq->pending_request;
> +	int ret;
> +
> +	if (!vq->iotlb_call_ctx)
> +		return -EOPNOTSUPP;
> +
> +	if (!vq->iotlb_request)
> +		return -EOPNOTSUPP;
> +
> +	if (pending->flags.type == VHOST_IOTLB_MISS) {
> +		return -EEXIST;
> +	}
> +
> +	pending->iova = iova;
> +	pending->flags.type = VHOST_IOTLB_MISS;
> +
> +	ret = __copy_to_user(vq->iotlb_request, pending,
> +			     sizeof(struct vhost_iotlb_entry));
> +	if (ret) {
> +		goto err;
> +	}
> +
> +	if (vq->iotlb_call_ctx)
> +		eventfd_signal(vq->iotlb_call_ctx, 1);
> +err:
> +	return ret;
> +}
> +
>  static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
> -			  struct iovec iov[], int iov_size)
> +			  struct iovec iov[], int iov_size, int access)
>  {
>  	const struct vhost_umem_node *node;
> -	struct vhost_umem *umem = vq->umem;
> +	struct vhost_dev *dev = vq->dev;
> +	struct vhost_umem *umem = dev->iotlb ? dev->iotlb : dev->umem;
>  	struct iovec *_iov;
>  	u64 s = 0;
>  	int ret = 0;
>  
> +	spin_lock(&dev->iotlb_lock);
> +
>  	while ((u64)len > s) {
>  		u64 size;
>  		if (unlikely(ret >= iov_size)) {
>  			ret = -ENOBUFS;
>  			break;
>  		}
> +
>  		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
>  							addr, addr + len - 1);
>  		if (node == NULL || node->start > addr) {
> -			ret = -EFAULT;
> +			if (umem != dev->iotlb) {
> +				ret = -EFAULT;
> +				break;
> +			}
> +			ret = -EAGAIN;
> +			break;
> +		} else if (!(node->perm & access)) {
> +			ret = -EPERM;
>  			break;
>  		}
> +
>  		_iov = iov + ret;
>  		size = node->size - addr + node->start;
>  		_iov->iov_len = min((u64)len - s, size);
> @@ -1228,6 +1450,10 @@ static int translate_desc(struct vhost_virtqueue
*vq, u64 addr, u32 len,
>  		++ret;
>  	}
>  
> +	spin_unlock(&dev->iotlb_lock);
> +
> +	if (ret == -EAGAIN)
> +		vhost_iotlb_miss(vq, addr);
>  	return ret;
>  }
>  
> @@ -1256,7 +1482,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  			struct iovec iov[], unsigned int iov_size,
>  			unsigned int *out_num, unsigned int *in_num,
>  			struct vhost_log *log, unsigned int *log_num,
> -			struct vring_desc *indirect)
> +			struct vring_desc *indirect, int access)
>  {
>  	struct vring_desc desc;
>  	unsigned int i = 0, count, found = 0;
> @@ -1274,9 +1500,10 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  	}
>  
>  	ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len,
vq->indirect,
> -			     UIO_MAXIOV);
> +			     UIO_MAXIOV, access);
>  	if (unlikely(ret < 0)) {
> -		vq_err(vq, "Translation failure %d in indirect.\n", ret);
> +		if (ret != -EAGAIN)
> +			vq_err(vq, "Translation failure %d in indirect.\n", ret);
>  		return ret;
>  	}
>  	iov_iter_init(&from, READ, vq->indirect, ret, len);
> @@ -1316,10 +1543,11 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  
>  		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
>  				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
> -				     iov_size - iov_count);
> +				     iov_size - iov_count, access);
>  		if (unlikely(ret < 0)) {
> -			vq_err(vq, "Translation failure %d indirect idx %d\n",
> -			       ret, i);
> +			if (ret != -EAGAIN)
> +				vq_err(vq, "Translation failure %d indirect idx %d\n",
> +					ret, i);
>  			return ret;
>  		}
>  		/* If this is an input descriptor, increment that count. */
> @@ -1355,7 +1583,8 @@ static int get_indirect(struct vhost_virtqueue *vq,
>  int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  		      struct iovec iov[], unsigned int iov_size,
>  		      unsigned int *out_num, unsigned int *in_num,
> -		      struct vhost_log *log, unsigned int *log_num)
> +		      struct vhost_log *log, unsigned int *log_num,
> +		      int access)
>  {
>  	struct vring_desc desc;
>  	unsigned int i, head, found = 0;
> @@ -1433,10 +1662,11 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
>  			ret = get_indirect(vq, iov, iov_size,
>  					   out_num, in_num,
> -					   log, log_num, &desc);
> +					   log, log_num, &desc, access);
>  			if (unlikely(ret < 0)) {
> -				vq_err(vq, "Failure detected "
> -				       "in indirect descriptor at idx %d\n", i);
> +				if (ret != -EAGAIN)
> +					vq_err(vq, "Failure detected "
> +						"in indirect descriptor at idx %d\n", i);
>  				return ret;
>  			}
>  			continue;
> @@ -1444,10 +1674,11 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  
>  		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
>  				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
> -				     iov_size - iov_count);
> +				     iov_size - iov_count, access);
>  		if (unlikely(ret < 0)) {
> -			vq_err(vq, "Translation failure %d descriptor idx %d\n",
> -			       ret, i);
> +			if (ret != -EAGAIN)
> +				vq_err(vq, "Translation failure %d descriptor idx %d\n",
> +					ret, i);
>  			return ret;
>  		}
>  		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 5d64393..4365104 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -62,13 +62,15 @@ struct vhost_umem_node {
>  	__u64 last;
>  	__u64 size;
>  	__u64 userspace_addr;
> -	__u64 flags_padding;
> +	__u32 perm;
> +	__u32 flags_padding;
>  	__u64 __subtree_last;
>  };
>  
>  struct vhost_umem {
>  	struct rb_root umem_tree;
>  	struct list_head umem_list;
> +	int numem;
>  };
>  
>  /* The virtqueue structure describes a queue attached to a device. */
> @@ -84,9 +86,13 @@ struct vhost_virtqueue {
>  	struct file *kick;
>  	struct file *call;
>  	struct file *error;
> +	struct file *iotlb_call;
>  	struct eventfd_ctx *call_ctx;
>  	struct eventfd_ctx *error_ctx;
>  	struct eventfd_ctx *log_ctx;
> +	struct eventfd_ctx *iotlb_call_ctx;
> +	struct vhost_iotlb_entry __user *iotlb_request;
> +	struct vhost_iotlb_entry pending_request;
>  
>  	struct vhost_poll poll;
>  
> @@ -135,6 +141,8 @@ struct vhost_virtqueue {
>  #endif
>  };
>  
> +#define VHOST_IOTLB_SIZE 2048
> +
>  struct vhost_dev {
>  	struct mm_struct *mm;
>  	struct mutex mutex;
> @@ -146,6 +154,8 @@ struct vhost_dev {
>  	struct list_head work_list;
>  	struct task_struct *worker;
>  	struct vhost_umem *umem;
> +	struct vhost_umem *iotlb;
> +	spinlock_t iotlb_lock;
>  };
>  
>  void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int
nvqs);
> @@ -164,7 +174,8 @@ int vhost_log_access_ok(struct vhost_dev *);
>  int vhost_get_vq_desc(struct vhost_virtqueue *,
>  		      struct iovec iov[], unsigned int iov_count,
>  		      unsigned int *out_num, unsigned int *in_num,
> -		      struct vhost_log *log, unsigned int *log_num);
> +		      struct vhost_log *log, unsigned int *log_num,
> +		      int access);
>  void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
>  
>  int vhost_init_used(struct vhost_virtqueue *);
> @@ -183,7 +194,7 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct
vhost_log *log,
>  		    unsigned int log_num, u64 len);
>  
>  #define vq_err(vq, fmt, ...) do {                                  \
> -		pr_debug(pr_fmt(fmt), ##__VA_ARGS__);       \
> +		printk(pr_fmt(fmt), ##__VA_ARGS__);       \
>  		if ((vq)->error_ctx)                               \
>  				eventfd_signal((vq)->error_ctx, 1);\
>  	} while (0)
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index 8d0c0df..5c0a22f 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -59,8 +59,9 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
>  	if (ULLONG_MAX - ctx->count < n)
>  		n = ULLONG_MAX - ctx->count;
>  	ctx->count += n;
> -	if (waitqueue_active(&ctx->wqh))
> +	if (waitqueue_active(&ctx->wqh)) {
>  		wake_up_locked_poll(&ctx->wqh, POLLIN);
> +	}
>  	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
>  
>  	return n;
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index ab373191..5c35ab4 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -47,6 +47,32 @@ struct vhost_vring_addr {
>  	__u64 log_guest_addr;
>  };
>  
> +struct vhost_iotlb_entry {
> +	__u64 iova;
> +	__u64 size;
> +	__u64 userspace_addr;
Alignment requirements?
> +	struct {
> +#define VHOST_ACCESS_RO      0x1
> +#define VHOST_ACCESS_WO      0x2
> +#define VHOST_ACCESS_RW      0x3
> +		__u8  perm;
> +#define VHOST_IOTLB_MISS           1
> +#define VHOST_IOTLB_UPDATE         2
> +#define VHOST_IOTLB_INVALIDATE     3
> +		__u8  type;
> +#define VHOST_IOTLB_INVALID        0x1
> +#define VHOST_IOTLB_VALID          0x2
> +		__u8  valid;
why do we need this flag?
> +		__u8  u8_padding;
> +		__u32 padding;
> +	} flags;
> +};
> +
> +struct vhost_vring_iotlb_entry {
> +	unsigned int index;
> +	__u64 userspace_addr;
> +};
> +
>  struct vhost_memory_region {
>  	__u64 guest_phys_addr;
>  	__u64 memory_size; /* bytes */
> @@ -127,6 +153,15 @@ struct vhost_memory {
>  /* Set eventfd to signal an error */
>  #define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct
vhost_vring_file)
>  
> +/* IOTLB */
> +/* Specify an eventfd file descriptor to signle on IOTLB miss */
typo
> +#define VHOST_SET_VRING_IOTLB_CALL _IOW(VHOST_VIRTIO, 0x23, struct      \
> +                                        vhost_vring_file)
> +#define VHOST_SET_VRING_IOTLB_REQUEST _IOW(VHOST_VIRTIO, 0x25, struct   \
> +                                           vhost_vring_iotlb_entry)
> +#define VHOST_UPDATE_IOTLB _IOW(VHOST_VIRTIO, 0x24, struct
vhost_iotlb_entry)
> +#define VHOST_RUN_IOTLB _IOW(VHOST_VIRTIO, 0x26, int)
> +
Is the assumption that userspace must dedicate a thread to running the iotlb? 
I dislike this one.
Please support asynchronous APIs at least optionally to make
userspace make its own threading decisions.
>  /* VHOST_NET specific defines */
>  
>  /* Attach virtio net ring to a raw socket, or tap device.
Don't we need a feature bit for this?
Are we short on feature bits? If yes maybe it's time to add
something like PROTOCOL_FEATURES that we have in vhost-user.
> -- 
> 2.5.0