? 2022/2/27 ??9:41, Eugenio P?rez ??:> 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 P?rez <eperezma at redhat.com>
> Reviewed-by: Peter Xu <peterx at redhat.com>
> ---
> 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);