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



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.


Daniel
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