Re: [PATCH 43/86] hppa: drop RAM size fixup

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 2 Jan 2020 13:06:33 +0100
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 1/2/20 12:31 PM, Helge Deller wrote:
> > On 31.12.19 16:44, Philippe Mathieu-Daudé wrote:  
> >> On 12/31/19 2:03 PM, Igor Mammedov wrote:  
> >>> If user provided non-sense RAM size, board will complain and
> >>> continue running with max RAM size supported.
> >>> Also RAM is going to be allocated by generic code, so it won't be
> >>> possible for board to fix things up for user.
> >>>
> >>> Make it error message and exit to force user fix CLI,
> >>> instead of accepting non-sense CLI values.
> >>>
> >>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> >>> ---
> >>>    hw/hppa/machine.c | 3 ++-
> >>>    1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/hw/hppa/machine.c b/hw/hppa/machine.c
> >>> index 5d0de26..25f5afc 100644
> >>> --- a/hw/hppa/machine.c
> >>> +++ b/hw/hppa/machine.c
> >>> @@ -92,7 +92,8 @@ static void machine_hppa_init(MachineState *machine)
> >>>          /* Limit main memory. */
> >>>        if (ram_size > FIRMWARE_START) {
> >>> -        machine->ram_size = ram_size = FIRMWARE_START;
> >>> +        error_report("RAM size more than %d is not supported", FIRMWARE_START);
> >>> +        exit(EXIT_FAILURE);  
> >>
> >> $ qemu-system-hppa -m 3841m
> >> qemu-system-hppa: invalid accelerator kvm
> >> qemu-system-hppa: falling back to tcg
> >> qemu-system-hppa: RAM size more than -268435456 is not supported
> >>
> >> Instead of using qemu_strtosz_MiB on FIRMWARE_START or unsigned format, we can simply use "RAM size more than 3840m is not supported". Is that OK with you?  
> > 
> > I don't really like that change.
> > 
> > We currently only emulate a 32-bit system, and for those 4GB is the maximum.
> > So, if I start my machine with "qemu-system-hppa -m 4G", the current code
> > then automatically uses the maximum possible of 3841MB (which is limited by
> > firmware start address).
> > I don't expect users to know the excact 3841MB number.
> > Even on a phyiscal machine you can only add DIMMs of sizes 2GB, 3GB or 4GB,
> > but not "3841MB".  
> 
> Thanks for the explanation. This deserves a comment in the source file 
> IMHO (and displaying a warning to the user that the behavior is changed).
> 
> I understand the CPU can't access this DRAM area because the ROM is 
> mapped there. What about other devices, can they do DMA access to it?
> 
> Igor: If this complicates your series too much, I think we can directly 
> allocate up-to 4GiB and not worry about the 256MiB lost.

Do you mean
s/"RAM size more than %d is not supported"/"RAM size more than 4Gb is not supported"/

> > So, I think that patch is - although it's more correct - not a
> > benefit for the end user.
> > 
> > Helge
> >   
> 
>