[RFC PATCH v2 5/5] softmmu/physmem: Have flaview API check MemTxAttrs::bus_perm field

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Check bus permission in flatview_access_allowed() before
running any bus transaction.

There is not change for the default case (MEMTXPERM_UNSPECIFIED).

The MEMTXPERM_UNRESTRICTED case works as an allow list. Devices
using it won't be checked by flatview_access_allowed().

The only deny list equivalent is MEMTXPERM_RAM_DEVICE: devices
using this flag will reject transactions and set the optional
MemTxResult to MEMTX_BUS_ERROR.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 softmmu/physmem.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 0d31a2f4199..329542dba75 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2772,7 +2772,22 @@ static inline bool flatview_access_allowed(MemoryRegion *mr, MemTxAttrs attrs,
                                            hwaddr addr, hwaddr len,
                                            MemTxResult *result)
 {
-    return true;
+    if (unlikely(attrs.bus_perm == MEMTXPERM_RAM_DEVICE)) {
+        if (memory_region_is_ram(mr) || memory_region_is_ram_device(mr)) {
+            return true;
+        }
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "Invalid access to non-RAM device at "
+                      "addr 0x%" HWADDR_PRIX ", size %" HWADDR_PRIu ", "
+                      "region '%s'\n", addr, len, memory_region_name(mr));
+        if (result) {
+            *result |= MEMTX_BUS_ERROR;
+        }
+        return false;
+    } else {
+        /* MEMTXPERM_UNRESTRICTED and MEMTXPERM_UNSPECIFIED cases */
+        return true;
+    }
 }
 
 /* Called within RCU critical section.  */
-- 
2.31.1