Re: [Qemu-trivial] [Qemu-devel] [PATCH v3] hw/i386/pc: prompt not multboot or morden kernel image

[Jesse Larrew <jlarrew@linux.vnet.ibm.com>]

On 04/08/2013 09:27 PM, liguang wrote:
> if head magic is missing or wrong unexpectedly, we'd
> better to prompt memssage for this.
> e.g.
> I make a mistake to boot a vmlinuz for MIPS(which
> I think it's for x86) like this:
> qemu-system-x86_64 -kernel vmlinuz -initrd demord
> then qemu report:
> "qemu: linux kernel too old to load a ram disk"
> that's misleading.
> 

Yes, that message would definitely be misleading in this case.

> Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
> ---
>  hw/i386/pc.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index ebbf059..6b29c3f 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -686,6 +686,8 @@ static void load_linux(void *fw_cfg,
>          if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename,
>                             kernel_cmdline, kernel_size, header)) {
>              return;
> +        } else {
> +            fprintf(stderr, "warn: invalid multiboot or modern kernel image\n");
>          }
>          protocol = 0;
>      }
> 

My impression from reading through the code is that this branch can be
legitimately triggered by an older kernel (protocol < 0x200). In that case,
the error message above would also be misleading.

I think a better solution might be to simply validate that the arch
specified in the ELF header matches the arch that qemu is emulating. I'll
look into this more tomorrow morning. :)

Jesse Larrew
Software Engineer, KVM Team
IBM Linux Technology Center
Phone: (512) 973-2052 (T/L: 363-2052)
jlarrew@linux.vnet.ibm.com