在 2021/10/30 上午2:35, Eugenio Pérez 写道:
This iova tree function allows it to look for a hole in allocated
regions and return a totally new translation for a given translated
address.
It's usage is mainly to allow devices to access qemu address space,
remapping guest's one into a new iova space where qemu can add chunks of
addresses.
Signed-off-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
---
include/qemu/iova-tree.h | 17 +++++
util/iova-tree.c | 139 +++++++++++++++++++++++++++++++++++++++
2 files changed, 156 insertions(+)
diff --git a/include/qemu/iova-tree.h b/include/qemu/iova-tree.h
index 8249edd764..33f9b2e13f 100644
--- a/include/qemu/iova-tree.h
+++ b/include/qemu/iova-tree.h
@@ -29,6 +29,7 @@
#define IOVA_OK (0)
#define IOVA_ERR_INVALID (-1) /* Invalid parameters */
#define IOVA_ERR_OVERLAP (-2) /* IOVA range overlapped */
+#define IOVA_ERR_NOMEM (-3) /* Cannot allocate */
I think we need a better name other than "NOMEM", since it's actually
means there's no sufficient hole for the range?
typedef struct IOVATree IOVATree;
typedef struct DMAMap {
@@ -119,6 +120,22 @@ const DMAMap *iova_tree_find_address(const IOVATree *tree, hwaddr iova);
*/
void iova_tree_foreach(IOVATree *tree, iova_tree_iterator iterator);
+/**
+ * iova_tree_alloc:
+ *
+ * @tree: the iova tree to allocate from
+ * @map: the new map (as translated addr & size) to allocate in iova region
+ * @iova_begin: the minimum address of the allocation
+ * @iova_end: the maximum addressable direction of the allocation
+ *
+ * Allocates a new region of a given size, between iova_min and iova_max.
+ *
+ * Return: Same as iova_tree_insert, but cannot overlap and can be out of
+ * free contiguous range. Caller can get the assigned iova in map->iova.
+ */
+int iova_tree_alloc(IOVATree *tree, DMAMap *map, hwaddr iova_begin,
+ hwaddr iova_end);
+
"iova_tree_alloc_map" seems better.
/**
* iova_tree_destroy:
*
diff --git a/util/iova-tree.c b/util/iova-tree.c
index 23ea35b7a4..27c921c4e2 100644
--- a/util/iova-tree.c
+++ b/util/iova-tree.c
@@ -16,6 +16,36 @@ struct IOVATree {
GTree *tree;
};
+/* Args to pass to iova_tree_alloc foreach function. */
+struct IOVATreeAllocArgs {
+ /* Size of the desired allocation */
+ size_t new_size;
+
+ /* The minimum address allowed in the allocation */
+ hwaddr iova_begin;
+
+ /* The last addressable allowed in the allocation */
+ hwaddr iova_last;
+
+ /* Previously-to-last iterated map, can be NULL in the first node */
+ const DMAMap *hole_left;
+
+ /* Last iterated map */
+ const DMAMap *hole_right;
Any reason we can move those to IOVATree structure, it can simplify a
lot of things.
+};
+
+/**
+ * Iterate args to tne next hole
+ *
+ * @args The alloc arguments
+ * @next The next mapping in the tree. Can be NULL to signal the last one
+ */
+static void iova_tree_alloc_args_iterate(struct IOVATreeAllocArgs *args,
+ const DMAMap *next) {
+ args->hole_left = args->hole_right;
+ args->hole_right = next;
+}
+
static int iova_tree_compare(gconstpointer a, gconstpointer b, gpointer data)
{
const DMAMap *m1 = a, *m2 = b;
@@ -107,6 +137,115 @@ int iova_tree_remove(IOVATree *tree, const DMAMap *map)
return IOVA_OK;
}
+/**
+ * Try to accomodate a map of size ret->size in a hole between
+ * max(end(hole_left), iova_start).
+ *
+ * @args Arguments to allocation
+ */
+static bool iova_tree_alloc_map_in_hole(const struct IOVATreeAllocArgs *args)
+{
+ const DMAMap *left = args->hole_left, *right = args->hole_right;
+ uint64_t hole_start, hole_last;
+
+ if (right && right->iova + right->size < args->iova_begin) {
+ return false;
+ }
+
+ if (left && left->iova > args->iova_last) {
+ return false;
+ }
+
+ hole_start = MAX(left ? left->iova + left->size + 1 : 0, args->iova_begin);
+ hole_last = MIN(right ? right->iova : HWADDR_MAX, args->iova_last);
+
+ if (hole_last - hole_start > args->new_size) {
+ /* We found a valid hole. */
+ return true;
+ }
+
+ /* Keep iterating */
+ return false;
+}
+
+/**
+ * Foreach dma node in the tree, compare if there is a hole wit its previous
+ * node (or minimum iova address allowed) and the node.
+ *
+ * @key Node iterating
+ * @value Node iterating
+ * @pargs Struct to communicate with the outside world
+ *
+ * Return: false to keep iterating, true if needs break.
+ */
+static gboolean iova_tree_alloc_traverse(gpointer key, gpointer value,
+ gpointer pargs)
+{
+ struct IOVATreeAllocArgs *args = pargs;
+ DMAMap *node = value;
+
+ assert(key == value);
+
+ iova_tree_alloc_args_iterate(args, node);
+ if (args->hole_left && args->hole_left->iova > args->iova_last) {
+ return true;
+ }
+
+ if (iova_tree_alloc_map_in_hole(args)) {
+ return true;
+ }
+
+ return false;
+}
+
+int iova_tree_alloc(IOVATree *tree, DMAMap *map, hwaddr iova_begin,
+ hwaddr iova_last)
+{
+ struct IOVATreeAllocArgs args = {
+ .new_size = map->size,
+ .iova_begin = iova_begin,
+ .iova_last = iova_last,
+ };
+
+ if (iova_begin == 0) {
+ /* Some devices does not like addr 0 */
+ iova_begin += qemu_real_host_page_size;
+ }
+
+ assert(iova_begin < iova_last);
+
+ /*
+ * Find a valid hole for the mapping
+ *
+ * Assuming low iova_begin, so no need to do a binary search to
+ * locate the first node.
+ *
+ * TODO: We can improve the search speed if we save the beginning and the
+ * end of holes, so we don't iterate over the previous saved ones.
+ *
+ * TODO: Replace all this with g_tree_node_first/next/last when available
+ * (from glib since 2.68). To do it with g_tree_foreach complicates the
+ * code a lot.
To say the truth, the codes in iova_tree_alloc_traverse() is hard to be
reviewed. I think it would be easy to use first/next/last. What we
really need is to calculate the hole between two ranges with handmade
first, last.
Thanks
+ *
+ */
+ g_tree_foreach(tree->tree, iova_tree_alloc_traverse, &args);
+ if (!iova_tree_alloc_map_in_hole(&args)) {
+ /*
+ * 2nd try: Last iteration left args->right as the last DMAMap. But
+ * (right, end) hole needs to be checked too
+ */
+ iova_tree_alloc_args_iterate(&args, NULL);
+ if (!iova_tree_alloc_map_in_hole(&args)) {
+ return IOVA_ERR_NOMEM;
+ }
+ }
+
+ map->iova = MAX(iova_begin,
+ args.hole_left ?
+ args.hole_left->iova + args.hole_left->size + 1 : 0);
+ return iova_tree_insert(tree, map);
+}
+
void iova_tree_destroy(IOVATree *tree)
{
g_tree_destroy(tree->tree);
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