Re: [Qemu-devel] [Qemu PATCH v2] add a boot option to do strict boot

[Eric Blake <eblake@redhat.com>]

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On 01/09/2013 01:39 AM, Amos Kong wrote:
> Current seabios will try to boot from selected devices first,
> if they are all failed, seabios will also try to boot from
> un-selected devices.
> 
> We need to make it configurable. I already posted a seabios
> patch to add a new device type to halt booting. Qemu can add
> "HALT" at the end of bootindex string, then seabios will halt
> booting after trying to boot from selected devices.
> 
> This option only effects when boot priority is changed by
> bootindex options, the old style(-boot order=..) will still
> try to boot from un-selected devices.
> 
> v2: add HALT entry in get_boot_devices_list()
>     define boot_strict to bool
> 
> Signed-off-by: Amos Kong <akong@redhat.com>
> ---

Libvirt will need to expose an attribute that lets the user control
whether to use this new option; how do we probe via QMP whether the new
-boot strict=on command-line option is available?

> +++ b/qemu-options.hx
> @@ -376,14 +376,14 @@ ETEXI
>  
>  DEF("boot", HAS_ARG, QEMU_OPTION_boot,
>      "-boot [order=drives][,once=drives][,menu=on|off]\n"
> -    "      [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time]\n"
> +    "      [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off]\n"
>      "                'drives': floppy (a), hard disk (c), CD-ROM (d), network (n)\n"
>      "                'sp_name': the file's name that would be passed to bios as logo picture, if menu=on\n"
>      "                'sp_time': the period that splash picture last if menu=on, unit is ms\n"
>      "                'rb_timeout': the timeout before guest reboot when boot failed, unit is ms\n",

So if I understand correctly, -boot order=... is incompatible with -boot
strict=on; even though you have listed both options under a single -boot
entry in the -help. We've already declared that -help output is no
longer guaranteed stable, so this doesn't really impact libvirt, but
would it make any more sense to list this as two orthogonal entries, to
make it clear that they don't mix?

-boot order=drivers[,once=drives]...
-boot strict=on|off[,menu=on|off]...

But this is all bikeshedding, so it's not worth a v3 if you disagree.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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