[PATCH] hw/block/pflash_cfi01: Restore ROMD mode after migration

pflash_post_load() did not restore the ROMD mode of the memory region.
Although cmd and wcycle are migrated, the destination retains the
default ROMD = true from realize.  When the source was in a non-array
mode (e.g. ID read, cmd = 0x90), reads on the destination bypass
pflash_read() via the ROM fast path and return raw storage bytes
instead of the command-specific response.

Derive ROMD from the migrated cmd/wcycle in pflash_post_load.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4042
Cc: [email protected]
Signed-off-by: Bin Guo <[email protected]>
---
 hw/block/pflash_cfi01.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index 5b9ddb20b1..a13b91967e 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -1030,6 +1030,16 @@ static int pflash_post_load(void *opaque, int version_id)
 {
     PFlashCFI01 *pfl = opaque;
 
+    /*
+     * ROMD mode is not in the VMState; derive it from the migrated
+     * cmd and wcycle.  Only (wcycle == 0, cmd == 0x00) is read-array.
+     */
+    if (pfl->wcycle == 0 && pfl->cmd == 0x00) {
+        memory_region_rom_device_set_romd(&pfl->mem, true);
+    } else {
+        memory_region_rom_device_set_romd(&pfl->mem, false);
+    }
+
     if (!pfl->ro) {
         pfl->vmstate = qemu_add_vm_change_state_handler(postload_update_cb,
                                                         pfl);
-- 
2.50.1 (Apple Git-155)