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authorPeter Crosthwaite <peter.crosthwaite@xilinx.com>2016-01-21 14:15:06 +0000
committerPeter Maydell <peter.maydell@linaro.org>2016-01-21 14:15:06 +0000
commitf0c02d15b57da6f5463e3768aa0cfeedccf4b8f4 (patch)
tree5b9ab0f89c38fce4e8097e2147cef945fbf65074 /memory.c
parent79ed0416477440ccb6acf136d6808a4f5848bbdf (diff)
memory: Add address_space_init_shareable()
This will either create a new AS or return a pointer to an already existing equivalent one, if we have already created an AS for the specified root memory region. The motivation is to reuse address spaces as much as possible. It's going to be quite common that bus masters out in device land have pointers to the same memory region for their mastering yet each will need to create its own address space. Let the memory API implement sharing for them. Aside from the perf optimisations, this should reduce the amount of redundant output on info mtree as well. Thee returned value will be malloced, but the malloc will be automatically freed when the AS runs out of refs. Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com> [PMM: dropped check for NULL root as unused; added doc-comment; squashed Peter C's reference-counting patch into this one; don't compare name string when deciding if we can share ASes; read as->malloced before the unref of as->root to avoid possible read-after-free if as->root was the owner of as] Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Diffstat (limited to 'memory.c')
-rw-r--r--memory.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/memory.c b/memory.c
index 93bd8ed7bc..d2d0a92810 100644
--- a/memory.c
+++ b/memory.c
@@ -2124,7 +2124,9 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
{
memory_region_ref(root);
memory_region_transaction_begin();
+ as->ref_count = 1;
as->root = root;
+ as->malloced = false;
as->current_map = g_new(FlatView, 1);
flatview_init(as->current_map);
as->ioeventfd_nb = 0;
@@ -2139,6 +2141,7 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
static void do_address_space_destroy(AddressSpace *as)
{
MemoryListener *listener;
+ bool do_free = as->malloced;
address_space_destroy_dispatch(as);
@@ -2150,12 +2153,36 @@ static void do_address_space_destroy(AddressSpace *as)
g_free(as->name);
g_free(as->ioeventfds);
memory_region_unref(as->root);
+ if (do_free) {
+ g_free(as);
+ }
+}
+
+AddressSpace *address_space_init_shareable(MemoryRegion *root, const char *name)
+{
+ AddressSpace *as;
+
+ QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) {
+ if (root == as->root && as->malloced) {
+ as->ref_count++;
+ return as;
+ }
+ }
+
+ as = g_malloc0(sizeof *as);
+ address_space_init(as, root, name);
+ as->malloced = true;
+ return as;
}
void address_space_destroy(AddressSpace *as)
{
MemoryRegion *root = as->root;
+ as->ref_count--;
+ if (as->ref_count) {
+ return;
+ }
/* Flush out anything from MemoryListeners listening in on this */
memory_region_transaction_begin();
as->root = NULL;