1 files changed, 57 insertions, 25 deletions

diff --git a/system/physmem.c b/system/physmem.c
index 94600a33ec..971bfa0855 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -3095,6 +3095,20 @@ void cpu_flush_icache_range(hwaddr start, hwaddr len)
                                      NULL, len, FLUSH_CACHE);
 }
 
+/*
+ * A magic value stored in the first 8 bytes of the bounce buffer struct. Used
+ * to detect illegal pointers passed to address_space_unmap.
+ */
+#define BOUNCE_BUFFER_MAGIC 0xb4017ceb4ffe12ed
+
+typedef struct {
+    uint64_t magic;
+    MemoryRegion *mr;
+    hwaddr addr;
+    size_t len;
+    uint8_t buffer[];
+} BounceBuffer;
+
 static void
 address_space_unregister_map_client_do(AddressSpaceMapClient *client)
 {
@@ -3120,9 +3134,9 @@ void address_space_register_map_client(AddressSpace *as, QEMUBH *bh)
     QEMU_LOCK_GUARD(&as->map_client_list_lock);
     client->bh = bh;
     QLIST_INSERT_HEAD(&as->map_client_list, client, link);
-    /* Write map_client_list before reading in_use.  */
+    /* Write map_client_list before reading bounce_buffer_size. */
     smp_mb();
-    if (!qatomic_read(&as->bounce.in_use)) {
+    if (qatomic_read(&as->bounce_buffer_size) < as->max_bounce_buffer_size) {
         address_space_notify_map_clients_locked(as);
     }
 }
@@ -3251,28 +3265,40 @@ void *address_space_map(AddressSpace *as,
     mr = flatview_translate(fv, addr, &xlat, &l, is_write, attrs);
 
     if (!memory_access_is_direct(mr, is_write)) {
-        if (qatomic_xchg(&as->bounce.in_use, true)) {
+        size_t used = qatomic_read(&as->bounce_buffer_size);
+        for (;;) {
+            hwaddr alloc = MIN(as->max_bounce_buffer_size - used, l);
+            size_t new_size = used + alloc;
+            size_t actual =
+                qatomic_cmpxchg(&as->bounce_buffer_size, used, new_size);
+            if (actual == used) {
+                l = alloc;
+                break;
+            }
+            used = actual;
+        }
+
+        if (l == 0) {
             *plen = 0;
             return NULL;
         }
-        /* Avoid unbounded allocations */
-        l = MIN(l, TARGET_PAGE_SIZE);
-        as->bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, l);
-        as->bounce.addr = addr;
-        as->bounce.len = l;
 
+        BounceBuffer *bounce = g_malloc0(l + sizeof(BounceBuffer));
+        bounce->magic = BOUNCE_BUFFER_MAGIC;
         memory_region_ref(mr);
-        as->bounce.mr = mr;
+        bounce->mr = mr;
+        bounce->addr = addr;
+        bounce->len = l;
+
         if (!is_write) {
             flatview_read(fv, addr, MEMTXATTRS_UNSPECIFIED,
-                          as->bounce.buffer, l);
+                          bounce->buffer, l);
         }
 
         *plen = l;
-        return as->bounce.buffer;
+        return bounce->buffer;
     }
 
-
     memory_region_ref(mr);
     *plen = flatview_extend_translation(fv, addr, len, mr, xlat,
                                         l, is_write, attrs);
@@ -3287,12 +3313,11 @@ void *address_space_map(AddressSpace *as,
 void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
                          bool is_write, hwaddr access_len)
 {
-    if (buffer != as->bounce.buffer) {
-        MemoryRegion *mr;
-        ram_addr_t addr1;
+    MemoryRegion *mr;
+    ram_addr_t addr1;
 
-        mr = memory_region_from_host(buffer, &addr1);
-        assert(mr != NULL);
+    mr = memory_region_from_host(buffer, &addr1);
+    if (mr != NULL) {
         if (is_write) {
             invalidate_and_set_dirty(mr, addr1, access_len);
         }
@@ -3302,15 +3327,22 @@ void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
         memory_region_unref(mr);
         return;
     }
+
+
+    BounceBuffer *bounce = container_of(buffer, BounceBuffer, buffer);
+    assert(bounce->magic == BOUNCE_BUFFER_MAGIC);
+
     if (is_write) {
-        address_space_write(as, as->bounce.addr, MEMTXATTRS_UNSPECIFIED,
-                            as->bounce.buffer, access_len);
-    }
-    qemu_vfree(as->bounce.buffer);
-    as->bounce.buffer = NULL;
-    memory_region_unref(as->bounce.mr);
-    /* Clear in_use before reading map_client_list.  */
-    qatomic_set_mb(&as->bounce.in_use, false);
+        address_space_write(as, bounce->addr, MEMTXATTRS_UNSPECIFIED,
+                            bounce->buffer, access_len);
+    }
+
+    qatomic_sub(&as->bounce_buffer_size, bounce->len);
+    bounce->magic = ~BOUNCE_BUFFER_MAGIC;
+    memory_region_unref(bounce->mr);
+    g_free(bounce);
+    /* Write bounce_buffer_size before reading map_client_list. */
+    smp_mb();
     address_space_notify_map_clients(as);
 }