memory: add address_space_access_valid

The old-style IOMMU lets you check whether an access is valid in a
given DMAContext.  There is no equivalent for AddressSpace in the
memory API, implement it with a lookup of the dispatch tree.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

dma-helpers.c

@@ -298,6 +298,11 @@ bool iommu_dma_memory_valid(DMAContext *dma, dma_addr_t addr, dma_addr_t len,
             plen = len;
         }
 
+        if (!address_space_access_valid(dma->as, paddr, len,
+                                        dir == DMA_DIRECTION_FROM_DEVICE)) {
+            return false;
+        }
+
         len -= plen;
         addr += plen;
     }

exec.c

@@ -2067,6 +2067,27 @@ static void cpu_notify_map_clients(void)
     }
 }
 
+bool address_space_access_valid(AddressSpace *as, hwaddr addr, int len, bool is_write)
+{
+    MemoryRegionSection *section;
+    hwaddr l, xlat;
+
+    while (len > 0) {
+        l = len;
+        section = address_space_translate(as, addr, &xlat, &l, is_write);
+        if (!memory_access_is_direct(section->mr, is_write)) {
+            l = memory_access_size(l, addr);
+            if (!memory_region_access_valid(section->mr, xlat, l, is_write)) {
+                return false;
+            }
+        }
+
+        len -= l;
+        addr += l;
+    }
+    return true;
+}
+
 /* Map a physical memory region into a host virtual address.
  * May map a subset of the requested range, given by and returned in *plen.
  * May return NULL if resources needed to perform the mapping are exhausted.

include/exec/memory.h

@@ -866,6 +866,21 @@ MemoryRegionSection *address_space_translate(AddressSpace *as, hwaddr addr,
                                              hwaddr *xlat, hwaddr *len,
                                              bool is_write);
 
+/* address_space_access_valid: check for validity of accessing an address
+ * space range
+ *
+ * Check whether memory is assigned to the given address space range.
+ *
+ * For now, addr and len should be aligned to a page size.  This limitation
+ * will be lifted in the future.
+ *
+ * @as: #AddressSpace to be accessed
+ * @addr: address within that address space
+ * @len: length of the area to be checked
+ * @is_write: indicates the transfer direction
+ */
+bool address_space_access_valid(AddressSpace *as, hwaddr addr, int len, bool is_write);
+
 /* address_space_map: map a physical memory region into a host virtual address
  *
  * May map a subset of the requested range, given by and returned in @plen.

include/sysemu/dma.h

@@ -113,7 +113,8 @@ static inline bool dma_memory_valid(DMAContext *dma,
                                     DMADirection dir)
 {
     if (!dma_has_iommu(dma)) {
-        return true;
+        return address_space_access_valid(dma->as, addr, len,
+                                          dir == DMA_DIRECTION_FROM_DEVICE);
     } else {
         return iommu_dma_memory_valid(dma, addr, len, dir);
     }