在 2022/2/27 下午9:41, 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>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
---
include/qemu/iova-tree.h | 18 ++++++
util/iova-tree.c | 133 +++++++++++++++++++++++++++++++++++++++
2 files changed, 151 insertions(+)
diff --git a/include/qemu/iova-tree.h b/include/qemu/iova-tree.h
index 8249edd764..a623136cd8 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 */
typedef struct IOVATree IOVATree;
typedef struct DMAMap {
@@ -119,6 +120,23 @@ const DMAMap *iova_tree_find_address(const IOVATree *tree, hwaddr iova);
*/
void iova_tree_foreach(IOVATree *tree, iova_tree_iterator iterator);
+/**
+ * iova_tree_alloc:
Should be iova_tree_alloc_map.
+ *
+ * @tree: the iova tree to allocate from
+ * @map: the new map (as translated addr & size) to allocate in the 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 return error if
+ * iova tree is out of free contiguous range. The caller gets the assigned iova
+ * in map->iova.
+ */
+int iova_tree_alloc_map(IOVATree *tree, DMAMap *map, hwaddr iova_begin,
+ hwaddr iova_end);
+
/**
* iova_tree_destroy:
*
diff --git a/util/iova-tree.c b/util/iova-tree.c
index 23ea35b7a4..302b01f1cc 100644
--- a/util/iova-tree.c
+++ b/util/iova-tree.c
@@ -16,6 +16,39 @@ 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;
+
+ /* Map at the left of the hole, can be NULL if "this" is first one */
+ const DMAMap *prev;
+
+ /* Map at the right of the hole, can be NULL if "prev" is the last one */
+ const DMAMap *this;
+
+ /* If found, we fill in the IOVA here */
+ hwaddr iova_result;
+
+ /* Whether have we found a valid IOVA */
+ bool iova_found;
+};
+
+/**
+ * Iterate args to the 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->prev = args->this;
+ args->this = next;
+}
+
static int iova_tree_compare(gconstpointer a, gconstpointer b, gpointer data)
{
const DMAMap *m1 = a, *m2 = b;
@@ -107,6 +140,106 @@ int iova_tree_remove(IOVATree *tree, const DMAMap *map)
return IOVA_OK;
}
+/**
+ * Try to find an unallocated IOVA range between prev and this elements.
+ *
+ * @args Arguments to allocation
+ *
+ * Cases:
+ *
+ * (1) !prev, !this: No entries allocated, always succeed
+ *
+ * (2) !prev, this: We're iterating at the 1st element.
+ *
+ * (3) prev, !this: We're iterating at the last element.
+ *
+ * (4) prev, this: this is the most common case, we'll try to find a hole
+ * between "prev" and "this" mapping.
+ *
+ * Note that this function assumes the last valid iova is HWADDR_MAX, but it
+ * searches linearly so it's easy to discard the result if it's not the case.
+ */
+static void iova_tree_alloc_map_in_hole(struct IOVATreeAllocArgs *args)
+{
+ const DMAMap *prev = args->prev, *this = args->this;
+ uint64_t hole_start, hole_last;
+
+ if (this && this->iova + this->size < args->iova_begin) {
+ return;
+ }
+
+ hole_start = MAX(prev ? prev->iova + prev->size + 1 : 0, args->iova_begin);
+ hole_last = this ? this->iova : HWADDR_MAX;
Do we need to use iova_last instead of HWADDR_MAX?
+
+ if (hole_last - hole_start > args->new_size) {
+ args->iova_result = hole_start;
+ args->iova_found = true;
+ }
+}
+
+/**
+ * Foreach dma node in the tree, compare if there is a hole with 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);
+ iova_tree_alloc_map_in_hole(args);
+ return args->iova_found;
+}
+
+int iova_tree_alloc_map(IOVATree *tree, DMAMap *map, hwaddr iova_begin,
+ hwaddr iova_last)
+{
+ struct IOVATreeAllocArgs args = {
+ .new_size = map->size,
+ .iova_begin = iova_begin,
+ };
+
+ assert(iova_begin < iova_last);
Should we use "<=" here, otherwise we disallow allocate the size of 1.
And maybe we should return error instead of assert.
+
+ /*
+ * 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: 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.
+ *
One more question
The current code looks work but still a little bit complicated to be
reviewed. Looking at the missing helpers above, if the add and remove
are seldom. I wonder if we can simply do
g_tree_foreach() during each add/del to build a sorted list then we can
emulate g_tree_node_first/next/last easily?
+ */
+ g_tree_foreach(tree->tree, iova_tree_alloc_traverse, &args);
+ if (!args.iova_found) {
+ /*
+ * Either tree is empty or the last hole is still not checked.
+ * g_tree_foreach does not compare (last, iova_end] range, so we check
"(last, iova_last]" ?
Thanks
+ * it here.
+ */
+ iova_tree_alloc_args_iterate(&args, NULL);
+ iova_tree_alloc_map_in_hole(&args);
+ }
+
+ if (!args.iova_found || args.iova_result + map->size > iova_last) {
+ return IOVA_ERR_NOMEM;
+ }
+
+ map->iova = args.iova_result;
+ return iova_tree_insert(tree, map);
+}
+
void iova_tree_destroy(IOVATree *tree)
{
g_tree_destroy(tree->tree);
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