Re: [Qemu-devel] nvram and boot order

[Anthony Liguori]

David Gibson <address@hidden> writes:

> On Thu, Oct 18, 2012 at 08:32:54AM +0200, Alexander Graf wrote:
>> 
>> 
>> On 18.10.2012, at 03:18, Benjamin Herrenschmidt <address@hidden> wrote:
>> 
>> > On Thu, 2012-10-18 at 11:09 +1100, David Gibson wrote:
>> > 
>> >>>> That's horrible; if you use -boot just once it will clobber a
>> >>>> persistent NVRAM's boot order.  I see that a means of changing the
>> >>>> default boot order from management tools is desirable, but that
>> >>>> shouldn't be the normal behaviour of -boot.  And the objections to (2)
>> >>>> apply even more strongly - we'd need to translate arbitrary -boot
>> >>>> strings to NVRAM representation which may not be at all
>> >>>> straightforward from the information qemu has available.
>> >>> 
>> >>> It may not be straight forward, but it's what makes the most sense from
>> >>> a user's PoV.
>> >> 
>> >> Bollocks.  Using -boot to override the normal boot sequence
>> >> permanently changing the normal boot sequence absoultely does not make
>> >> sense from a user's PoV.
>> > 
>> > I strongly agree with David here. -boot should not change the persistent
>> > state.
>> 
>> I think Anthony and you are looking at 2 different use cases, each
>> with their own sane reasoning.
>> 
>> You want to have the chance to override the boot order temporarily
>> for things like cd boot or quick guest rescue missions.
>> 
>> You also want to be able to permanently change the guest's boot
>> order from a management tool. At that same place you want to be able
>> to display it, so you don't have to boot your vm to know what it
>> would be doing.
>
> That's true to an extent.  However, I vehemently disagree that it's
> arbitrary which one gets the new option.  Neither -boot nor bootindex=
> alter any persistent data now and they should not suddenly start doing
> so.

That's not true.

For the PC, -boot modifies the CMOS memory.  If we persisted CMOS, then
-boot would cause a persistent modification in the boot order.

Regards,

Anthony Liguori