Re: [Qemu-devel] [PATCH 2/5] exec: qemu_ram_alloc_device, qemu_ram_resize

[Paolo Bonzini <pbonzini@redhat.com>]

On 19/11/2014 15:26, Dr. David Alan Gilbert wrote:
> * Paolo Bonzini (pbonzini@redhat.com) wrote:
>>
>>
>> On 19/11/2014 15:13, Dr. David Alan Gilbert wrote:
>>> Since we've wondered off the actual ACPI table stuff into general
>>> ROM sizing, I'd like to propose some concrete fixes:
>>>
>>>   1) We explicitly name the bios file in a .romfile attribute for
>>>      all ROMs.
>>>   2) The code that uses .romfile has an expansion for $MACHINETYPE
>>>   3) We actually symlink all of those together, anyone who wants/has
>>>      to deal with different versions can downstream.
>>>   4) The machine types contain size attributes for the ROMs that
>>>      are generoously larger than the ROMs anyone currently uses.
>>>
>>> I think 1..3 should deal with those of us who have to deal with different
>>> ROM versions on different machine types.
>>
>> It should, but it's a solution in search of a problem.
> 
> Well we already do something close to 1 & 2 downstream but more ad-hoc;
> it's just a generalisation (and 4 from padding the size of our images).
> So we already had that problem.

Upstream too.  See pxe-* vs. efi-* NIC option ROMs.  The latter includes
both PXE firmware for BIOS and EFI drivers.  We keep two copies because
they have different sizes.  Having explicit expansions for $MACHINETYPE
would be hugely overkill, in my opinion.

Paolo

>>
>>> 4 might be good enough for the ACPI tables if you can bound it.
>>
>> Already doing that (rounding to 128k, warning if >64k), but it is not a
>> definitive solution.
>>
>> We also do (4) for ROMs, since VGA BIOSes use only 36k out of 64k and
>> iPXE ROMs use only ~200k out of 256k.
>>
>> Paolo
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>