[RFC v3 21/29] vhost: Add VhostIOVATree

[Eugenio Pérez]

This tree is able to look for a translated address from a IOVA address.

At first glance is similar to util/iova-tree. However, SVQ working on
devices with limited IOVA space need more capabilities, like allocating
IOVA chunks or perform reverse translations (qemu addresses to iova).

Starting a sepparated implementation. Knowing than insertions/deletions
will not be as frequent as searches, it uses an ordered array at
implementation. A different name could be used, but ordered
searchable array is a little bit long though.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-iova-tree.h |  50 ++++++++++
 hw/virtio/vhost-iova-tree.c | 188 ++++++++++++++++++++++++++++++++++++
 hw/virtio/meson.build       |   2 +-
 3 files changed, 239 insertions(+), 1 deletion(-)
 create mode 100644 hw/virtio/vhost-iova-tree.h
 create mode 100644 hw/virtio/vhost-iova-tree.c

diff --git a/hw/virtio/vhost-iova-tree.h b/hw/virtio/vhost-iova-tree.h
new file mode 100644
index 0000000000..2a44af8b3a
--- /dev/null
+++ b/hw/virtio/vhost-iova-tree.h
@@ -0,0 +1,50 @@
+/*
+ * vhost software live migration ring
+ *
+ * SPDX-FileCopyrightText: Red Hat, Inc. 2021
+ * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_VIRTIO_VHOST_IOVA_TREE_H
+#define HW_VIRTIO_VHOST_IOVA_TREE_H
+
+#include <gmodule.h>
+
+#include "exec/memory.h"
+
+typedef struct VhostDMAMap {
+    void *translated_addr;
+    hwaddr iova;
+    hwaddr size;                /* Inclusive */
+    IOMMUAccessFlags perm;
+} VhostDMAMap;
+
+typedef enum VhostDMAMapNewRC {
+    VHOST_DMA_MAP_OVERLAP = -2,
+    VHOST_DMA_MAP_INVALID = -1,
+    VHOST_DMA_MAP_OK = 0,
+} VhostDMAMapNewRC;
+
+/**
+ * VhostIOVATree
+ *
+ * Store and search IOVA -> Translated mappings.
+ *
+ * Note that it cannot remove nodes.
+ */
+typedef struct VhostIOVATree {
+    /* Ordered array of reverse translations, IOVA address to qemu memory. */
+    GArray *iova_taddr_map;
+} VhostIOVATree;
+
+void vhost_iova_tree_new(VhostIOVATree *iova_rm);
+void vhost_iova_tree_destroy(VhostIOVATree *iova_rm);
+
+const VhostDMAMap *vhost_iova_tree_find_taddr(const VhostIOVATree *iova_rm,
+                                              const VhostDMAMap *map);
+VhostDMAMapNewRC vhost_iova_tree_insert(VhostIOVATree *iova_rm,
+                                        VhostDMAMap *map);
+
+#endif
diff --git a/hw/virtio/vhost-iova-tree.c b/hw/virtio/vhost-iova-tree.c
new file mode 100644
index 0000000000..dfd7e448b5
--- /dev/null
+++ b/hw/virtio/vhost-iova-tree.c
@@ -0,0 +1,188 @@
+/*
+ * vhost software live migration ring
+ *
+ * SPDX-FileCopyrightText: Red Hat, Inc. 2021
+ * SPDX-FileContributor: Author: Eugenio Pérez <eperezma@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "vhost-iova-tree.h"
+
+#define G_ARRAY_NOT_ZERO_TERMINATED false
+#define G_ARRAY_NOT_CLEAR_ON_ALLOC false
+
+/**
+ * Inserts an element after an existing one in garray.
+ *
+ * @array      The array
+ * @prev_elem  The previous element of array of NULL if prepending
+ * @map        The DMA map
+ *
+ * It provides the aditional advantage of being type safe over
+ * g_array_insert_val, which accepts a reference pointer instead of a value
+ * with no complains.
+ */
+static void vhost_iova_tree_insert_after(GArray *array,
+                                         const VhostDMAMap *prev_elem,
+                                         const VhostDMAMap *map)
+{
+    size_t pos;
+
+    if (!prev_elem) {
+        pos = 0;
+    } else {
+        pos = prev_elem - &g_array_index(array, typeof(*prev_elem), 0) + 1;
+    }
+
+    g_array_insert_val(array, pos, *map);
+}
+
+static gint vhost_iova_tree_cmp_iova(gconstpointer a, gconstpointer b)
+{
+    const VhostDMAMap *m1 = a, *m2 = b;
+
+    if (m1->iova > m2->iova + m2->size) {
+        return 1;
+    }
+
+    if (m1->iova + m1->size < m2->iova) {
+        return -1;
+    }
+
+    /* Overlapped */
+    return 0;
+}
+
+/**
+ * Find the previous node to a given iova
+ *
+ * @array  The ascending ordered-by-translated-addr array of VhostDMAMap
+ * @map    The map to insert
+ * @prev   Returned location of the previous map
+ *
+ * Return VHOST_DMA_MAP_OK if everything went well, or VHOST_DMA_MAP_OVERLAP if
+ * it already exists. It is ok to use this function to check if a given range
+ * exists, but it will use a linear search.
+ *
+ * TODO: We can use bsearch to locate the entry if we save the state in the
+ * needle, knowing that the needle is always the first argument to
+ * compare_func.
+ */
+static VhostDMAMapNewRC vhost_iova_tree_find_prev(const GArray *array,
+                                                  GCompareFunc compare_func,
+                                                  const VhostDMAMap *map,
+                                                  const VhostDMAMap **prev)
+{
+    size_t i;
+    int r;
+
+    *prev = NULL;
+    for (i = 0; i < array->len; ++i) {
+        r = compare_func(map, &g_array_index(array, typeof(*map), i));
+        if (r == 0) {
+            return VHOST_DMA_MAP_OVERLAP;
+        }
+        if (r < 0) {
+            return VHOST_DMA_MAP_OK;
+        }
+
+        *prev = &g_array_index(array, typeof(**prev), i);
+    }
+
+    return VHOST_DMA_MAP_OK;
+}
+
+/**
+ * Create a new IOVA tree
+ *
+ * @tree  The IOVA tree
+ */
+void vhost_iova_tree_new(VhostIOVATree *tree)
+{
+    assert(tree);
+
+    tree->iova_taddr_map = g_array_new(G_ARRAY_NOT_ZERO_TERMINATED,
+                                       G_ARRAY_NOT_CLEAR_ON_ALLOC,
+                                       sizeof(VhostDMAMap));
+}
+
+/**
+ * Destroy an IOVA tree
+ *
+ * @tree  The iova tree
+ */
+void vhost_iova_tree_destroy(VhostIOVATree *tree)
+{
+    g_array_unref(g_steal_pointer(&tree->iova_taddr_map));
+}
+
+/**
+ * Perform a search on a GArray.
+ *
+ * @array Glib array
+ * @map Map to look up
+ * @compare_func Compare function to use
+ *
+ * Return The found element or NULL if not found.
+ *
+ * This can be replaced with g_array_binary_search (Since glib 2.62) when that
+ * is common enough.
+ */
+static const VhostDMAMap *vhost_iova_tree_bsearch(const GArray *array,
+                                                  const VhostDMAMap *map,
+                                                  GCompareFunc compare_func)
+{
+    return bsearch(map, array->data, array->len, sizeof(*map), compare_func);
+}
+
+/**
+ * Find the translated address stored from a IOVA address
+ *
+ * @tree  The iova tree
+ * @map   The map with the memory address
+ *
+ * Return the stored mapping, or NULL if not found.
+ */
+const VhostDMAMap *vhost_iova_tree_find_taddr(const VhostIOVATree *tree,
+                                              const VhostDMAMap *map)
+{
+    return vhost_iova_tree_bsearch(tree->iova_taddr_map, map,
+                                  vhost_iova_tree_cmp_iova);
+}
+
+/**
+ * Insert a new map
+ *
+ * @tree  The iova tree
+ * @map   The iova map
+ *
+ * Returns:
+ * - VHOST_DMA_MAP_OK if the map fits in the container
+ * - VHOST_DMA_MAP_INVALID if the map does not make sense (like size overflow)
+ * - VHOST_DMA_MAP_OVERLAP if the tree already contains that map
+ * Can query the assignated iova in map.
+ */
+VhostDMAMapNewRC vhost_iova_tree_insert(VhostIOVATree *tree,
+                                        VhostDMAMap *map)
+{
+    const VhostDMAMap *prev;
+    int find_prev_rc;
+
+    if (map->translated_addr + map->size < map->translated_addr ||
+        map->iova + map->size < map->iova || map->perm == IOMMU_NONE) {
+        return VHOST_DMA_MAP_INVALID;
+    }
+
+    /* Check for duplicates, and save position for insertion */
+    find_prev_rc = vhost_iova_tree_find_prev(tree->iova_taddr_map,
+                                             vhost_iova_tree_cmp_iova, map,
+                                             &prev);
+    if (find_prev_rc == VHOST_DMA_MAP_OVERLAP) {
+        return VHOST_DMA_MAP_OVERLAP;
+    }
+
+    vhost_iova_tree_insert_after(tree->iova_taddr_map, prev, map);
+    return VHOST_DMA_MAP_OK;
+}
diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
index 8b5a0225fe..cb306b83c6 100644
--- a/hw/virtio/meson.build
+++ b/hw/virtio/meson.build
@@ -11,7 +11,7 @@ softmmu_ss.add(when: 'CONFIG_ALL', if_true: 
files('vhost-stub.c'))
 
 virtio_ss = ss.source_set()
 virtio_ss.add(files('virtio.c'))
-virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 
'vhost-backend.c', 'vhost-shadow-virtqueue.c'))
+virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c', 
'vhost-backend.c', 'vhost-shadow-virtqueue.c', 'vhost-iova-tree.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_USER', if_true: files('vhost-user.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_VDPA', if_true: files('vhost-vdpa.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true: 
files('virtio-balloon.c'))
-- 
2.27.0