Re: [PATCH 0/7] hw/arm/raspi4b: Add models with 4GB and 8GB of DRAM

[Daniel P . Berrangé]

On Mon, Feb 03, 2025 at 02:45:06PM +0000, Peter Maydell wrote:
> On Mon, 3 Feb 2025 at 14:33, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > On Mon, Feb 03, 2025 at 02:29:49PM +0000, Alex Bennée wrote:
> > > Peter Maydell <peter.maydell@linaro.org> writes:
> > >
> > > > On Sat, 1 Feb 2025 at 12:57, BALATON Zoltan <balaton@eik.bme.hu> wrote:
> > > >>
> > > >> On Sat, 1 Feb 2025, Philippe Mathieu-Daudé wrote:
> > > >> > - Deprecate the 'raspi4b' machine name, renaming it as
> > > >> >  'raspi4b-1g' on 32-bit hosts, 'raspi4b-2g' otherwise.
> > > >> > - Add the 'raspi4b-4g' and 'raspi4b-8g' machines, with
> > > >> >  respectively 4GB and 8GB of DRAM.
> > > >>
> > > >> IMHO (meaning you can ignore it, just my opinion) if the only 
> > > >> difference
> > > >> is the memory size -machine raspi4b -memory 4g would be better user
> > > >> experience than having a lot of different machines.
> > > >
> > > > Yes, I think I agree. We have a way for users to specify
> > > > how much memory they want, and I think it makes more sense
> > > > to use that than to have lots of different machine types.
> > >
> > > I guess for the Pi we should validate the -memory supplied is on of the
> > > supported grid of devices rather than an arbitrary value?
> >
> > If the user wants to create a rpi4 with 6 GB RAM why should we stop
> > them ? It is their choice if they want to precisely replicate RAM
> > size from a physical model, or use something different when virtualized.
> 
> The board revision code (reported to the guest via the emulated
> firmware interface) only supports reporting 256MB, 512MB,
> 1GB, 2GB, 4GB or 8GB:
> 
> https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#new-style-revision-codes

I think it would be valid to report the revision code for the memory
size that doesn't exceed what QEMU has configured. eg if configured
with 6 GB, then report code for 4 GB. 

> For Arm embedded boards we mostly tend to "restrict the user
> to what you can actually do", except for older boards where
> we tended not to write any kind of sanity checking on CPU
> type, memory size, etc.

If we're going to strictly limit memory size that's accepted I wonder
how we could information users/mgmt apps about what's permitted ?

Expressing valid combinations of configs across different args gets
pretty complicated quickly :-(


With regards,
Daniel
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