Re: [Qemu-devel] 128Kb bios size and older machines?

[Michael Tokarev <mjt@tls.msk.ru>]

06.02.2014 12:50, Gerd Hoffmann wrote:
> On Do, 2014-02-06 at 12:28 +0400, Michael Tokarev wrote:
>> Since the "small" (128Kb) seabios is now built without
>> support of xen, does that mean that xen will be unable
>> to use qemu with -M 1.7 and before?  Does it _ever_ use
>> -M option like this?
> 
> As far I know xen has its own seabios builds anyway as they
> have to add hvmloader to the mix.  Thats why it has been
> turned off in the upstream blob builds, nobody will use these
> with xen anyway.

Thank you Gerd for the answer.  Ian, can you give some light
here, what is still missing in seabios for xen?  Because,
well, ..

> Not sure how all that is organized in the debian xen/seabios packages.

.. debian uses upstream seabios directly with xen now, not
the one which comes from xen repository.

(And yes I know about
  http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=5f2875739beef3a75c7a7e8579b6cbcb464e61b3
which talks about >128kb bios size.  This is actually exactly
the same issue which I'm trying to address now, from a few PoVs:
qemu now builds/uses stripped-down bios for older (pre-2.0) machine
types, and that stripped-down version does not include Xen bits
in order to fit in 128Kb, because with xen it doesn't fit anymore.
Maybe we should start building special xen variant of seabios --
stripped down but WITH xen.  Oh well.)

Thanks,

/mjt

>> I'm asking because I don't really understand how this works.
>>  We updated seabios in debian to 1.7.4 (with qemu 1.7), it
>> grew past 128Kb, and now I'm trying to understand what
>> exactly is broken and how to fix it.  I should either
>> build it w/o xen support for it to fit in 128Kb again,
>> or keep it at larger size and live with (migration) breakage
>> caused by different bios size.
> 
> Turn off xhci should be enough to make it fit into 128k again (used to
> be the case for me last time I tried).
> 
>> BTW, recompiling seabios-1.7.4 without xchi and a few other
>> recently added stuff (pvscsi boot et al) with gcc-4.7.2 on
>> debian does not produce 128Kb binary, it is larger than 128k,
>> so I can't produce 128kb bios on debian anymore.. ;)
> 
> Hmm.  I had the same problem with gcc 4.4 on rhel6, but gcc 4.7+ works
> for me.  No idea, sorry.
> 
> cheers,
>   Gerd
> 
>