[Qemu-devel] [PATCH] hw/block: report when pflash backing file isn't aligned

["Alex Bennée" <alex.bennee@linaro.org>]

It looks like there was going to be code to check we had some sort of
alignment so lets replace it with an actual check. This is a bit more
useful than the enigmatic "failed to read the initial flash content"
when we attempt to read the number of bytes the device should have.

This is a potential confusing stumbling block when you move from using
-bios to using -drive if=pflash,file=blob,format=raw,readonly for
loading your firmware code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 hw/block/pflash_cfi01.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index bffb4c40e7..f3251b236c 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -722,12 +722,19 @@ static void pflash_cfi01_realize(DeviceState *dev, Error **errp)
     }
     device_len = sector_len_per_device * blocks_per_device;
 
-    /* XXX: to be fixed */
-#if 0
-    if (total_len != (8 * 1024 * 1024) && total_len != (16 * 1024 * 1024) &&
-        total_len != (32 * 1024 * 1024) && total_len != (64 * 1024 * 1024))
-        return NULL;
-#endif
+    /*
+     * Validate the backing store is the right size for pflash
+     * devices. It has to be padded to a multiple of the flash block
+     * size.
+     */
+    if (pfl->blk) {
+        uint64_t backing_len = blk_getlength(pfl->blk);
+        if (device_len != backing_len) {
+            error_setg(errp, "backing file wrong size "
+                       "(%" PRId64 " != %" PRId64")", backing_len, device_len);
+            return;
+        }
+    }
 
     memory_region_init_rom_device(
         &pfl->mem, OBJECT(dev),
-- 
2.20.1