[Qemu-block] [PATCH v3 2/9] hw/block/pflash_cfi01: Use the correct READ_ARRAY value

[Philippe Mathieu-Daudé]

In the "Read Array Flowchart" the command has a value of 0xFF.

In the document [*] the "Read Array Flowchart", the READ_ARRAY
command has a value of 0xff.

Use the correct value in the pflash model.

There is no change of behavior in the guest, because:
- when the guest were sending 0xFF, the reset_flash label
  was setting the command value as 0x00
- 0x00 was used internally for READ_ARRAY

To keep migration behaving correctly, we have to increase
the VMState version. When migrating from an older version,
we use the correct command value.

[*] "Common Flash Interface (CFI) and Command Sets"
    (Intel Application Note 646)
    Appendix B "Basic Command Set"

Reviewed-by: John Snow <address@hidden>
Reviewed-by: Alistair Francis <address@hidden>
Regression-tested-by: Laszlo Ersek <address@hidden>
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
v3: Handle migrating the 'cmd' field.

Since Laszlo stated he did not test migration [*], I'm keeping his
test tag, because the change with v2 has no impact in the tests
he ran.

Likewise I'm keeping John and Alistair tags, but I'd like an extra
review for the migration change, thanks!

[*] https://lists.gnu.org/archive/html/qemu-devel/2019-07/msg00679.html
---
 hw/block/pflash_cfi01.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index 9e34fd4e82..58cbef0588 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -100,7 +100,7 @@ static int pflash_post_load(void *opaque, int version_id);
 
 static const VMStateDescription vmstate_pflash = {
     .name = "pflash_cfi01",
-    .version_id = 1,
+    .version_id = 2,
     .minimum_version_id = 1,
     .post_load = pflash_post_load,
     .fields = (VMStateField[]) {
@@ -277,10 +277,9 @@ static uint32_t pflash_read(PFlashCFI01 *pfl, hwaddr 
offset,
         /* This should never happen : reset state & treat it as a read */
         DPRINTF("%s: unknown command state: %x\n", __func__, pfl->cmd);
         pfl->wcycle = 0;
-        pfl->cmd = 0;
+        pfl->cmd = 0xff;
         /* fall through to read code */
-    case 0x00:
-        /* Flash area read */
+    case 0xff: /* Read Array */
         ret = pflash_data_read(pfl, offset, width, be);
         break;
     case 0x10: /* Single byte program */
@@ -448,8 +447,6 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
     case 0:
         /* read mode */
         switch (cmd) {
-        case 0x00: /* ??? */
-            goto reset_flash;
         case 0x10: /* Single Byte Program */
         case 0x40: /* Single Byte Program */
             DPRINTF("%s: Single Byte Program\n", __func__);
@@ -526,7 +523,7 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
             if (cmd == 0xd0) { /* confirm */
                 pfl->wcycle = 0;
                 pfl->status |= 0x80;
-            } else if (cmd == 0xff) { /* read array mode */
+            } else if (cmd == 0xff) { /* Read Array */
                 goto reset_flash;
             } else
                 goto error_flash;
@@ -553,7 +550,7 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
             } else if (cmd == 0x01) {
                 pfl->wcycle = 0;
                 pfl->status |= 0x80;
-            } else if (cmd == 0xff) {
+            } else if (cmd == 0xff) { /* read array mode */
                 goto reset_flash;
             } else {
                 DPRINTF("%s: Unknown (un)locking command\n", __func__);
@@ -645,7 +642,7 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
     trace_pflash_reset();
     memory_region_rom_device_set_romd(&pfl->mem, true);
     pfl->wcycle = 0;
-    pfl->cmd = 0;
+    pfl->cmd = 0xff;
 }
 
 
@@ -761,7 +758,7 @@ static void pflash_cfi01_realize(DeviceState *dev, Error 
**errp)
     }
 
     pfl->wcycle = 0;
-    pfl->cmd = 0;
+    pfl->cmd = 0xff;
     pfl->status = 0;
     /* Hardcoded CFI table */
     /* Standard "QRY" string */
@@ -1001,5 +998,11 @@ static int pflash_post_load(void *opaque, int version_id)
         pfl->vmstate = qemu_add_vm_change_state_handler(postload_update_cb,
                                                         pfl);
     }
+    if (version_id < 2) {
+        /* v1 used incorrect value of 0x00 for the READ_ARRAY command. */
+        if (pfl->cmd == 0x00) {
+            pfl->cmd =  0xff;
+        }
+    }
     return 0;
 }
-- 
2.20.1