memory: Move AddressSpaceDispatch from AddressSpace to FlatView

As we are going to share FlatView's between AddressSpace's,
and AddressSpaceDispatch is a structure to perform quick lookup
in FlatView, this moves ASD to FlatView.

After previosly open coded ASD rendering, we can also remove
as->next_dispatch as the new FlatView pointer is stored
on a stack and set to an AS atomically.

flatview_destroy() is executed under RCU instead of
address_space_dispatch_free() now.

This makes mem_begin/mem_commit to work with ASD and mem_add with FV
as later on mem_add will be taking FV as an argument anyway.

This should cause no behavioural change.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-Id: <20170921085110.25598-5-aik@ozlabs.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 11 insertions, 30 deletions

diff --git a/exec.c b/exec.c
index 1626d254bb..afd64127e6 100644
--- a/exec.c
+++ b/exec.c
@@ -187,8 +187,6 @@ typedef struct PhysPageMap {
 } PhysPageMap;
 
 struct AddressSpaceDispatch {
-    struct rcu_head rcu;
-
     MemoryRegionSection *mru_section;
     /* This is a multi-level map on the physical address space.
      * The bottom level has pointers to MemoryRegionSections.
@@ -485,7 +483,7 @@ static MemoryRegionSection address_space_do_translate(AddressSpace *as,
     IOMMUMemoryRegionClass *imrc;
 
     for (;;) {
-        AddressSpaceDispatch *d = atomic_rcu_read(&as->dispatch);
+        AddressSpaceDispatch *d = address_space_to_dispatch(as);
         section = address_space_translate_internal(d, addr, &addr, plen, is_mmio);
 
         iommu_mr = memory_region_get_iommu(section->mr);
@@ -1222,7 +1220,7 @@ hwaddr memory_region_section_get_iotlb(CPUState *cpu,
     } else {
         AddressSpaceDispatch *d;
 
-        d = atomic_rcu_read(&section->address_space->dispatch);
+        d = address_space_to_dispatch(section->address_space);
         iotlb = section - d->map.sections;
         iotlb += xlat;
     }
@@ -1347,9 +1345,9 @@ static void register_multipage(AddressSpaceDispatch *d,
     phys_page_set(d, start_addr >> TARGET_PAGE_BITS, num_pages, section_index);
 }
 
-void mem_add(AddressSpace *as, MemoryRegionSection *section)
+void mem_add(AddressSpace *as, FlatView *fv, MemoryRegionSection *section)
 {
-    AddressSpaceDispatch *d = as->next_dispatch;
+    AddressSpaceDispatch *d = flatview_to_dispatch(fv);
     MemoryRegionSection now = *section, remain = *section;
     Int128 page_size = int128_make64(TARGET_PAGE_SIZE);
 
@@ -2672,7 +2670,7 @@ static void io_mem_init(void)
                           NULL, UINT64_MAX);
 }
 
-void mem_begin(AddressSpace *as)
+AddressSpaceDispatch *mem_begin(AddressSpace *as)
 {
     AddressSpaceDispatch *d = g_new0(AddressSpaceDispatch, 1);
     uint16_t n;
@@ -2688,26 +2686,19 @@ void mem_begin(AddressSpace *as)
 
     d->phys_map  = (PhysPageEntry) { .ptr = PHYS_MAP_NODE_NIL, .skip = 1 };
     d->as = as;
-    as->next_dispatch = d;
+
+    return d;
 }
 
-static void address_space_dispatch_free(AddressSpaceDispatch *d)
+void address_space_dispatch_free(AddressSpaceDispatch *d)
 {
     phys_sections_free(&d->map);
     g_free(d);
 }
 
-void mem_commit(AddressSpace *as)
+void mem_commit(AddressSpaceDispatch *d)
 {
-    AddressSpaceDispatch *cur = as->dispatch;
-    AddressSpaceDispatch *next = as->next_dispatch;
-
-    phys_page_compact_all(next, next->map.nodes_nb);
-
-    atomic_rcu_set(&as->dispatch, next);
-    if (cur) {
-        call_rcu(cur, address_space_dispatch_free, rcu);
-    }
+    phys_page_compact_all(d, d->map.nodes_nb);
 }
 
 static void tcg_commit(MemoryListener *listener)
@@ -2723,21 +2714,11 @@ static void tcg_commit(MemoryListener *listener)
      * We reload the dispatch pointer now because cpu_reloading_memory_map()
      * may have split the RCU critical section.
      */
-    d = atomic_rcu_read(&cpuas->as->dispatch);
+    d = address_space_to_dispatch(cpuas->as);
     atomic_rcu_set(&cpuas->memory_dispatch, d);
     tlb_flush(cpuas->cpu);
 }
 
-void address_space_destroy_dispatch(AddressSpace *as)
-{
-    AddressSpaceDispatch *d = as->dispatch;
-
-    atomic_rcu_set(&as->dispatch, NULL);
-    if (d) {
-        call_rcu(d, address_space_dispatch_free, rcu);
-    }
-}
-
 static void memory_map_init(void)
 {
     system_memory = g_malloc(sizeof(*system_memory));