address_space_read: address_space_to_flatview needs RCU lock

address_space_read is calling address_space_to_flatview but it can
be called outside the RCU lock.  To fix it, push the rcu_read_lock/unlock
pair up from flatview_read_full to address_space_read's constant size
fast path and address_space_read_full.

Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 25 insertions, 13 deletions

diff --git a/exec.c b/exec.c
index ec91162..e4552ee 100644
--- a/exec.c
+++ b/exec.c
@@ -2616,6 +2616,8 @@ static const MemoryRegionOps watch_mem_ops = {
     },
 };
 
+static MemTxResult flatview_read(FlatView *fv, hwaddr addr,
+                                      MemTxAttrs attrs, uint8_t *buf, int len);
 static MemTxResult flatview_write(FlatView *fv, hwaddr addr, MemTxAttrs attrs,
                                   const uint8_t *buf, int len);
 static bool flatview_access_valid(FlatView *fv, hwaddr addr, int len,
@@ -3165,24 +3167,18 @@ MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
     return result;
 }
 
-MemTxResult flatview_read_full(FlatView *fv, hwaddr addr,
-                               MemTxAttrs attrs, uint8_t *buf, int len)
+/* Called from RCU critical section.  */
+static MemTxResult flatview_read(FlatView *fv, hwaddr addr,
+                                 MemTxAttrs attrs, uint8_t *buf, int len)
 {
     hwaddr l;
     hwaddr addr1;
     MemoryRegion *mr;
-    MemTxResult result = MEMTX_OK;
-
-    if (len > 0) {
-        rcu_read_lock();
-        l = len;
-        mr = flatview_translate(fv, addr, &addr1, &l, false);
-        result = flatview_read_continue(fv, addr, attrs, buf, len,
-                                        addr1, l, mr);
-        rcu_read_unlock();
-    }
 
-    return result;
+    l = len;
+    mr = flatview_translate(fv, addr, &addr1, &l, false);
+    return flatview_read_continue(fv, addr, attrs, buf, len,
+                                  addr1, l, mr);
 }
 
 static MemTxResult flatview_rw(FlatView *fv, hwaddr addr, MemTxAttrs attrs,
@@ -3203,6 +3199,22 @@ MemTxResult address_space_rw(AddressSpace *as, hwaddr addr,
                        addr, attrs, buf, len, is_write);
 }
 
+MemTxResult address_space_read_full(AddressSpace *as, hwaddr addr,
+                                    MemTxAttrs attrs, uint8_t *buf, int len)
+{
+    MemTxResult result = MEMTX_OK;
+    FlatView *fv;
+
+    if (len > 0) {
+        rcu_read_lock();
+        fv = address_space_to_flatview(as);
+        result = flatview_read(fv, addr, attrs, buf, len);
+        rcu_read_unlock();
+    }
+
+    return result;
+}
+
 MemTxResult address_space_write(AddressSpace *as, hwaddr addr,
                                 MemTxAttrs attrs,
                                 const uint8_t *buf, int len)