diff options
| -rw-r--r-- | memory.c | 79 |
1 files changed, 69 insertions, 10 deletions
@@ -29,12 +29,26 @@ static unsigned memory_region_transaction_depth; static bool memory_region_update_pending; static bool global_dirty_log = false; +/* flat_view_mutex is taken around reading as->current_map; the critical + * section is extremely short, so I'm using a single mutex for every AS. + * We could also RCU for the read-side. + * + * The BQL is taken around transaction commits, hence both locks are taken + * while writing to as->current_map (with the BQL taken outside). + */ +static QemuMutex flat_view_mutex; + static QTAILQ_HEAD(memory_listeners, MemoryListener) memory_listeners = QTAILQ_HEAD_INITIALIZER(memory_listeners); static QTAILQ_HEAD(, AddressSpace) address_spaces = QTAILQ_HEAD_INITIALIZER(address_spaces); +static void memory_init(void) +{ + qemu_mutex_init(&flat_view_mutex); +} + typedef struct AddrRange AddrRange; /* @@ -225,6 +239,7 @@ struct FlatRange { * order. */ struct FlatView { + unsigned ref; FlatRange *ranges; unsigned nr; unsigned nr_allocated; @@ -246,6 +261,7 @@ static bool flatrange_equal(FlatRange *a, FlatRange *b) static void flatview_init(FlatView *view) { + view->ref = 1; view->ranges = NULL; view->nr = 0; view->nr_allocated = 0; @@ -279,6 +295,18 @@ static void flatview_destroy(FlatView *view) g_free(view); } +static void flatview_ref(FlatView *view) +{ + atomic_inc(&view->ref); +} + +static void flatview_unref(FlatView *view) +{ + if (atomic_fetch_dec(&view->ref) == 1) { + flatview_destroy(view); + } +} + static bool can_merge(FlatRange *r1, FlatRange *r2) { return int128_eq(addrrange_end(r1->addr), r2->addr.start) @@ -578,6 +606,17 @@ static void address_space_add_del_ioeventfds(AddressSpace *as, } } +static FlatView *address_space_get_flatview(AddressSpace *as) +{ + FlatView *view; + + qemu_mutex_lock(&flat_view_mutex); + view = as->current_map; + flatview_ref(view); + qemu_mutex_unlock(&flat_view_mutex); + return view; +} + static void address_space_update_ioeventfds(AddressSpace *as) { FlatView *view; @@ -587,7 +626,7 @@ static void address_space_update_ioeventfds(AddressSpace *as) AddrRange tmp; unsigned i; - view = as->current_map; + view = address_space_get_flatview(as); FOR_EACH_FLAT_RANGE(fr, view) { for (i = 0; i < fr->mr->ioeventfd_nb; ++i) { tmp = addrrange_shift(fr->mr->ioeventfds[i].addr, @@ -609,6 +648,7 @@ static void address_space_update_ioeventfds(AddressSpace *as) g_free(as->ioeventfds); as->ioeventfds = ioeventfds; as->ioeventfd_nb = ioeventfd_nb; + flatview_unref(view); } static void address_space_update_topology_pass(AddressSpace *as, @@ -676,14 +716,25 @@ static void address_space_update_topology_pass(AddressSpace *as, static void address_space_update_topology(AddressSpace *as) { - FlatView *old_view = as->current_map; + FlatView *old_view = address_space_get_flatview(as); FlatView *new_view = generate_memory_topology(as->root); address_space_update_topology_pass(as, old_view, new_view, false); address_space_update_topology_pass(as, old_view, new_view, true); + qemu_mutex_lock(&flat_view_mutex); + flatview_unref(as->current_map); as->current_map = new_view; - flatview_destroy(old_view); + qemu_mutex_unlock(&flat_view_mutex); + + /* Note that all the old MemoryRegions are still alive up to this + * point. This relieves most MemoryListeners from the need to + * ref/unref the MemoryRegions they get---unless they use them + * outside the iothread mutex, in which case precise reference + * counting is necessary. + */ + flatview_unref(old_view); + address_space_update_ioeventfds(as); } @@ -1148,12 +1199,13 @@ void memory_region_sync_dirty_bitmap(MemoryRegion *mr) FlatRange *fr; QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) { - FlatView *view = as->current_map; + FlatView *view = address_space_get_flatview(as); FOR_EACH_FLAT_RANGE(fr, view) { if (fr->mr == mr) { MEMORY_LISTENER_UPDATE_REGION(fr, as, Forward, log_sync); } } + flatview_unref(view); } } @@ -1205,7 +1257,7 @@ static void memory_region_update_coalesced_range_as(MemoryRegion *mr, AddressSpa AddrRange tmp; MemoryRegionSection section; - view = as->current_map; + view = address_space_get_flatview(as); FOR_EACH_FLAT_RANGE(fr, view) { if (fr->mr == mr) { section = (MemoryRegionSection) { @@ -1231,6 +1283,7 @@ static void memory_region_update_coalesced_range_as(MemoryRegion *mr, AddressSpa } } } + flatview_unref(view); } static void memory_region_update_coalesced_range(MemoryRegion *mr) @@ -1532,7 +1585,7 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr, as = memory_region_to_address_space(root); range = addrrange_make(int128_make64(addr), int128_make64(size)); - view = as->current_map; + view = address_space_get_flatview(as); fr = flatview_lookup(view, range); if (!fr) { return ret; @@ -1553,6 +1606,7 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr, ret.readonly = fr->readonly; memory_region_ref(ret.mr); + flatview_unref(view); return ret; } @@ -1561,10 +1615,11 @@ void address_space_sync_dirty_bitmap(AddressSpace *as) FlatView *view; FlatRange *fr; - view = as->current_map; + view = address_space_get_flatview(as); FOR_EACH_FLAT_RANGE(fr, view) { MEMORY_LISTENER_UPDATE_REGION(fr, as, Forward, log_sync); } + flatview_unref(view); } void memory_global_dirty_log_start(void) @@ -1596,7 +1651,7 @@ static void listener_add_address_space(MemoryListener *listener, } } - view = as->current_map; + view = address_space_get_flatview(as); FOR_EACH_FLAT_RANGE(fr, view) { MemoryRegionSection section = { .mr = fr->mr, @@ -1610,6 +1665,7 @@ static void listener_add_address_space(MemoryListener *listener, listener->region_add(listener, §ion); } } + flatview_unref(view); } void memory_listener_register(MemoryListener *listener, AddressSpace *filter) @@ -1643,6 +1699,10 @@ void memory_listener_unregister(MemoryListener *listener) void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name) { + if (QTAILQ_EMPTY(&address_spaces)) { + memory_init(); + } + memory_region_transaction_begin(); as->root = root; as->current_map = g_new(FlatView, 1); @@ -1664,9 +1724,8 @@ void address_space_destroy(AddressSpace *as) memory_region_transaction_commit(); QTAILQ_REMOVE(&address_spaces, as, address_spaces_link); address_space_destroy_dispatch(as); - flatview_destroy(as->current_map); + flatview_unref(as->current_map); g_free(as->name); - g_free(as->current_map); g_free(as->ioeventfds); } |