Re: [Qemu-devel] Minimum RAM size for PC machines?

[David Hildenbrand <david@redhat.com>]

On 23.03.2017 09:19, Gerd Hoffmann wrote:
> On Mi, 2017-03-22 at 11:19 +0100, David Hildenbrand wrote:
>> On 22.03.2017 11:03, Thomas Huth wrote:
>>> On 22.03.2017 10:08, Markus Armbruster wrote:
>>> [...]
>>>> Are we now ready to accept a simple & stupid patch that actually helps
>>>> users, say letting boards that care declare minimum and maximum RAM
>>>> size?  And make PC reject RAM size less than 1MiB, even though "someone"
>>>> might conceivably have firmware that works with less?
>>>
>>> I'd say enforce a minimum RAM size on the normal "pc" and "q35" machine,
>>> but still allow smaller sizes on the "isapc" machine. So if "someone"
>>> comes around and claims to have a legacy firmware that wants less memory
>>> than 1MiB, just point them to the isapc machine.
>>> Just my 0.02 €.
>>>
>>>  Thomas
>>
>> Or maybe simply warn the user that things may go wrong instead of
>> enforcing it.
> 
> Why bother?  I have my doubts physical i440fx works with less than 1M
> either, given that this memory is needed to shadow the roms.  Possibly
> you can't even find dimms that are small to plug them into such a system
> to try ...

Because it seems to work if you supply the correct rom. We are trying to
catch user errors, don't we?

> 
> I'd say just add a hard limit and be done with it.

"640K ought to be enough for anybody". Any limit we set will become out
of date.

> 
> Maybe exclude isapc.  That one hasn't shadow support so things have at
> least a chance to work with less than 1M of memory.  But honestly I'd
> rather drop isapc, together with ia64 and sparc.  I mean, what is the
> use case?  'pc' machine type is compatible enough with vga and ide ports
> being on the standard isa locations so even msdos which has no pci
> support at all boots happily.

I think I like that idea.

> cheers,
>   Gerd
> 


-- 

Thanks,

David