Re: [PATCH 1/9] hw/hppa/machine: Allow up to 3840 MB total memory

[Helge Deller]

On 1/4/24 20:58, BALATON Zoltan wrote:
> On Thu, 4 Jan 2024, deller@kernel.org wrote:
> > From: Helge Deller <deller@gmx.de>
> >
> > The physical hardware allows DIMMs of 4 MB size and above, allowing up
> > to 3840 MB of memory, but is restricted by setup code to 3 GB.
> > Increase the limit to allow up to the maximum amount of memory.
> >
> > Btw. the memory area from 0xf000.0000 to 0xffff.ffff is reserved by
> > the architecture for firmware and I/O memory and can not be used for
> > standard memory.
> >
> > Signed-off-by: Helge Deller <deller@gmx.de>
> > Noticed-by: Nelson H. F. Beebe <beebe@math.utah.edu>
> > Fixes: b7746b1194c8 ("hw/hppa/machine: Restrict the total memory size to 3GB")
> > ---
> > hw/hppa/machine.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/hppa/machine.c b/hw/hppa/machine.c
> > index c8da7c18d5..6181f4b747 100644
> > --- a/hw/hppa/machine.c
> > +++ b/hw/hppa/machine.c
> > @@ -276,6 +276,7 @@ static TranslateFn 
> > *machine_HP_common_init_cpus(MachineState *machine)
> >     unsigned int smp_cpus = machine->smp.cpus;
> >     TranslateFn *translate;
> >     MemoryRegion *cpu_region;
> > +    ram_addr_t ram_max;
> >
> >     /* Create CPUs.  */
> >     for (unsigned int i = 0; i < smp_cpus; i++) {
> > @@ -288,8 +289,10 @@ static TranslateFn 
> > *machine_HP_common_init_cpus(MachineState *machine)
> >      */
> >     if (hppa_is_pa20(&cpu[0]->env)) {
> >         translate = translate_pa20;
> > +        ram_max = 0xf0000000;      /* 3.75 GB (limited by 32-bit firmware) */
> >     } else {
> >         translate = translate_pa10;
> > +        ram_max = 0xf0000000;      /* 3.75 GB (32-bit CPU) */
>
> If the value is the same what's the point of setting it here and not
> once above at definition? It is's only the different comment then you
> could have a comment saying "3.75 GB, limited by 32-bit firmware on
> 64 bit CPU" or similar there.

Oh, sorry, I missed to explain it...

qemu already supports the 64-bit CPU (hppa64), but using more than
3.75 GB of RAM is limited because the 32-bit firmware (which is
currently shipped) only supports up to max. 4GB.
For more than 4GB, a 64-bit SeaBIOS-hppa firmware is needed.
The current SeaBIOS-hppa git tree already contains the code
to build the firmware with 64-bit support. It already boots up,
but I still need some more bug-fixing until it can be used.

So, keeping two different lines here helps to more easily test
the 64-bit firmware and the final commit to allow more than 4GB
will become a one-liner with an upcoming patch.

Helge