[PATCH] softmmu/physmem: Improve guest memory allocation failure error message

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

When Linux refuses to overcommit a seriously wild allocation we get:

  $ qemu-system-i386 -m 40000000
  qemu-system-i386: cannot set up guest memory 'pc.ram': Cannot allocate memory

Slighly improve the error message, displaying the memory size
requested (in case the user didn't expect unspecified memory size
unit is in MiB):

  $ qemu-system-i386 -m 40000000
  qemu-system-i386: Cannot set up 38.1 TiB of guest memory 'pc.ram': Cannot allocate memory

Reported-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 softmmu/physmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 2e18947598e..2f300a9e79b 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1982,8 +1982,10 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
                                                   &new_block->mr->align,
                                                   shared, noreserve);
             if (!new_block->host) {
+                g_autofree char *size_s = size_to_str(new_block->max_length);
                 error_setg_errno(errp, errno,
-                                 "cannot set up guest memory '%s'",
+                                 "Cannot set up %s of guest memory '%s'",
+                                 size_s,
                                  memory_region_name(new_block->mr));
                 qemu_mutex_unlock_ramlist();
                 return;
-- 
2.31.1