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Tsirkin" , Peter Xu , virtualization@lists.linux-foundation.org, Eli Cohen , Eric Blake , Parav Pandit , Cindy Lu , "Fangyi \(Eric\)" , Markus Armbruster , yebiaoxiang@huawei.com, Liuxiangdong , Stefano Garzarella , Laurent Vivier , Eduardo Habkost , Richard Henderson , Gautam Dawar , Xiao W Wang , Stefan Hajnoczi , Juan Quintela , Harpreet Singh Anand , Paolo Bonzini , Lingshan Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 > Reviewed-by: Peter Xu > --- > 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);