Re: [Qemu-ppc] [PATCH] Workaround to bypass default qemu boot devices passed to SLOF

[Alexander Graf]

On 05.10.2012, at 13:41, Nikunj A Dadhania wrote:

> On Fri, 5 Oct 2012 12:24:47 +0200, Alexander Graf <address@hidden> wrote:
>> 
>> 
>> On 05.10.2012, at 10:29, Avik Sil <address@hidden> wrote:
>> 
>>> Hi David,
>>> 
>>> Please find below the patch for working around the default boot device 
>>> issue currently being discussed on the list.
>>> 
>>> Regards,
>>> Avik
>>> ---
>>> 
>>> The default qemu boot_devices string passed to firmware is "cad"
>>> which creates a confusion whether -boot oprion is specified or
>>> not. This patch handles this issue by setting a global flag when
>>> no -boot option is specified.
>> 
>> Hrm. How does x86 distinguish between -boot and bootindex=?
> 
> IMHO, that behaviour is not changed with this patch. Not sure how
> seabios is taking care of this.

I don't care about what you change with the patch. I care about consistency. 
And we shouldn't differ from x86 in that respect.

So please try and figure out how x86 knows that bootindex= is supposed to be 
used instead of -boot. We want the same logic for ppc.

> 
>> Also, we could just map -boot c to "nvram given boot device or first
>> automatically found disk". Then there's no need to know whether a
>> default was given. If you specify -boot you most likely want to force
>> cd-rom or network boot anyway and there is no way to tell which disk
>> 'c' would reflect.
> 
> We do want to use -boot [cad], but not for the nvram saved
> boot-device. That is done automatically in SLOF. If there is a property
> saved named boot-device, its going to use that for booting.

Hrm. Ok, how about we change the default string to

  xcad

with x meaning "device stored in nvram". Then any time you specify -boot it 
would override the nvram device, but you could also manually specify "I want to 
only boot from the nvram device, no fallbacks".


Alex

> The point here is when we really want to over-ride the boot-device
> setting in nvram(say the boot-device specified got corrupted), we need
> help from -boot and corresponding disk provided in the qemu
> command-line. 
> 
> At present, if there is boot-device specified there is now way to
> over-ride it using qemu command line as "cad" is passed by
> default. Which is the cause of all the pain. 
> 
> Regards,
> Nikunj
>