[PATCH v2 1/1] system/physmem: Improve guest memory allocation failure error message

[Bin Meng <bin.meng@processmission.com>]

From: 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

Slightly 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>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Bin Meng <bin.meng@processmission.com>

---

Changes in v2:
- Rebase onto current master
- Update the source path from softmmu/physmem.c to system/physmem.c
- Fix a typo in the commit message
- Collect Peter Xu's Reviewed-by and Bin Meng's Tested-by

 system/physmem.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/system/physmem.c b/system/physmem.c
index 362a00f76c..89ce6479f1 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2171,8 +2171,10 @@ 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;
-- 
2.53.0