Re: [PATCH-for-6.0] hw/ppc/mac_newworld: Restrict RAM to 2 GiB

[Philippe Mathieu-Daudé]

On 4/7/21 3:11 PM, Mark Cave-Ayland wrote:
> On 06/04/2021 09:48, Philippe Mathieu-Daudé wrote:
> 
>> On Mac99 and newer machines, the Uninorth PCI host bridge maps
>> the PCI hole region at 2GiB, so the RAM area beside 2GiB is not
>> accessible by the CPU. Restrict the memory to 2GiB to avoid
>> problems such the one reported in the buglink.
>>
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1922391
>> Reported-by: Håvard Eidnes <he@NetBSD.org>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>   hw/ppc/mac_newworld.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/hw/ppc/mac_newworld.c b/hw/ppc/mac_newworld.c
>> index 21759628466..d88b38e9258 100644
>> --- a/hw/ppc/mac_newworld.c
>> +++ b/hw/ppc/mac_newworld.c
>> @@ -157,6 +157,10 @@ static void ppc_core99_init(MachineState *machine)
>>       }
>>         /* allocate RAM */
>> +    if (machine->ram_size > 2 * GiB) {
>> +        error_report("RAM size more than 2 GiB is not supported");
>> +        exit(1);
>> +    }
>>       memory_region_add_subregion(get_system_memory(), 0, machine->ram);
>>         /* allocate and load firmware ROM */
> 
> I think the patch is correct, however I'm fairly sure that the default
> g3beige machine also has the PCI hole located at 0x80000000 so the same
> problem exists there too.
> 
> Also are you keen to get this merged for 6.0? It doesn't seem to solve a
> security issue/release blocker and I'm sure the current behaviour has
> been like this for a long time...

No problem. I wanted to revisit this bug anyway, I realized during the
night, while this patch makes QEMU exit cleanly, it hides the bug which
is likely in TYPE_MACIO_IDE (I haven't tried Håvard's full reproducer).

Regards,

Phil.