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-rw-r--r--hw/sd/sd.c25
1 files changed, 25 insertions, 0 deletions
diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index edd60a09c0..76d68359a4 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -32,6 +32,7 @@
 
 #include "qemu/osdep.h"
 #include "qemu/units.h"
+#include "qemu/cutils.h"
 #include "hw/irq.h"
 #include "hw/registerfields.h"
 #include "sysemu/block-backend.h"
@@ -2106,11 +2107,35 @@ static void sd_realize(DeviceState *dev, Error **errp)
     }
 
     if (sd->blk) {
+        int64_t blk_size;
+
         if (blk_is_read_only(sd->blk)) {
             error_setg(errp, "Cannot use read-only drive as SD card");
             return;
         }
 
+        blk_size = blk_getlength(sd->blk);
+        if (blk_size > 0 && !is_power_of_2(blk_size)) {
+            int64_t blk_size_aligned = pow2ceil(blk_size);
+            char *blk_size_str;
+
+            blk_size_str = size_to_str(blk_size);
+            error_setg(errp, "Invalid SD card size: %s", blk_size_str);
+            g_free(blk_size_str);
+
+            blk_size_str = size_to_str(blk_size_aligned);
+            error_append_hint(errp,
+                              "SD card size has to be a power of 2, e.g. %s.\n"
+                              "You can resize disk images with"
+                              " 'qemu-img resize <imagefile> <new-size>'\n"
+                              "(note that this will lose data if you make the"
+                              " image smaller than it currently is).\n",
+                              blk_size_str);
+            g_free(blk_size_str);
+
+            return;
+        }
+
         ret = blk_set_perm(sd->blk, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE,
                            BLK_PERM_ALL, errp);
         if (ret < 0) {