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



On 01/09/2013 01:02 PM, Daniel P. Berrange wrote:
> On Wed, Jan 09, 2013 at 12:36:52PM -0500, Laine Stump wrote:
>> On 01/09/2013 10:52 AM, Amos Kong wrote:
>>> On Wed, Jan 09, 2013 at 08:14:07AM -0700, Eric Blake wrote:
>>>> 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?
>>> Old style to adjust boot priority by order parameter:
>>> -boot order=n,strict=on (BAD, unselected devices will be tried)
>>>
>>> New style to adjust boot priority by bootindex:
>>> -device virtio-net-pci,...,bootindex=1 -boot strict=on (OK)
>>>
>>> We only want strict option to support new style.
>>>
>>> (those two styles are implemented in two different way insider
>>> seabios, the latest simple patch only changed the bootindex way)
>> Just a note about this: as far as I can tell virt-manager currently only
>> uses the "old style" of specifying boot order; it needs to be enhanced
>> to recognize the presence of bootindex=n ordering, and behave
>> accordingly. Looking from the outside, that looks to be not completely
>> trivial, as the old style of ordering only allows specifying "hard disk"
>> as a single line in the priority order, but the new style has each disk
>> specified separately. Not only that, but *which* of the disks is tried
>> first under the old order may change depending on whether or not a
>> bootmenu is requested (in one case it picks unit=0 on the controller, in
>> the other case, it orders the disks alphabetically by target dev name)
> Hmm, well libvirt should be using bootindex=n on the QEMU command line
> regardless of what applications put in the XML. ie if the application
> uses the old style XML, libvirt should translate that into bootindex=n
> for them.

Good point. WHerever it's changed though, it will be a bit tricky to
preserve current behavior, due to the idiosyncrasies I noted above.


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