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Re: [Qemu-devel] [PATCH v6] Add optionrom compatible with fw_cfg DMA ver

From: Richard W.M. Jones
Subject: Re: [Qemu-devel] [PATCH v6] Add optionrom compatible with fw_cfg DMA version
Date: Tue, 10 May 2016 18:36:24 +0100
User-agent: Mutt/1.5.20 (2009-12-10)

On Tue, May 10, 2016 at 07:24:28PM +0200, Paolo Bonzini wrote:
> On 09/05/2016 18:48, Richard W.M. Jones wrote:
> > 
> > Of course we're well outside any standards here.  Can we tell clang
> > users to use the GCC/pre-compiled option ROMs :-?  Any other ideas?  I
> > don't think I've missed a flag (GCC has -fno-toplevel-reorder, but
> > clang 3.8 doesn't ...)
> I guess the checksumming script (scripts/signrom.py) could take care of
> padding the file to a multiple of 512 bytes, and fill in the size in the
> third byte.  Then "_end" would not be necessary anymore and -m16 could
> replace the .code16 directive.

In my rather limited testing on gcc, gcc -m16 broke booting.  However
I've not investigated this further.  I'll do so shortly.

However I have a question: is there a formal standard or documentation
for the option ROM format?  Are we sticking to the (ancient) "BIOS Boot
Specification" or is there something newer?  (My copy is from 1996).


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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