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

[Bin Meng]

On Fri, Aug 20, 2021 at 11:52 PM Philippe Mathieu-Daudé
<philmd@redhat.com> wrote:
>
> 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

typo: Slightly

> 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);

Does g_autofree work with every compiler we support?

Looks it only applies to GCC and clang?
https://www.gitmemory.com/issue/linuxwacom/libwacom/142/518787578

>                  error_setg_errno(errp, errno,
> -                                 "cannot set up guest memory '%s'",
> +                                 "Cannot set up %s of guest memory '%s'",
> +                                 size_s,

Nice improvement!

>                                   memory_region_name(new_block->mr));
>                  qemu_mutex_unlock_ramlist();
>                  return;

Tested-by: Bin Meng <bmeng.cn@gmail.com>