Re: [Qemu-devel] [PATCH] spapr: make sure RMA is in first mode of first memory node

[Alexander Graf]

On 04.11.2013, at 11:55, Benjamin Herrenschmidt <address@hidden> wrote:

> On Mon, 2013-11-04 at 11:44 +0100, Alexander Graf wrote:
>> On 01.11.2013, at 11:21, Alexey Kardashevskiy <address@hidden> wrote:
>> 
>>> SLOF gets really confused if RTAS/device-tree and everything else
>>> what SLOF can use is not in the very first block of the very first
>>> memory node.
>>> 
>>> This makes sure that the RMA area is where SLOF expects it to be.
>>> 
>>> Cc: Benjamin Herrenschmidt <address@hidden>
>>> Cc: Nikunj A Dadhania <address@hidden>
>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>> ---
>>> hw/ppc/spapr.c | 8 +++++++-
>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>> index 09dc635..09a5d94 100644
>>> --- a/hw/ppc/spapr.c
>>> +++ b/hw/ppc/spapr.c
>>> @@ -1113,7 +1113,7 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
>>>    int i;
>>>    MemoryRegion *sysmem = get_system_memory();
>>>    MemoryRegion *ram = g_new(MemoryRegion, 1);
>>> -    hwaddr rma_alloc_size;
>>> +    hwaddr rma_alloc_size, node0_size;
>>>    uint32_t initrd_base = 0;
>>>    long kernel_size = 0, initrd_size = 0;
>>>    long load_limit, rtas_limit, fw_size;
>>> @@ -1154,6 +1154,12 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
>>>            spapr->rma_size = MIN(spapr->rma_size, 0x10000000);
>>>        }
>>>    }
>>> +    /*
>>> +     * SLOF gets confused if RMA resides not in the first block
>>> +     * of the first memory node so let's fix it.
>>> +     */
>>> +    node0_size = (nb_numa_nodes > 1) ? node_mem[0] : ram_size;
>>> +    spapr->rma_size = MIN(spapr->rma_size, node0_size);
>> 
>> So if I create a NUMA node of 4MB that will be my RMA? That sounds pretty 
>> broken, especially on 970.
>> 
>> Why does SLOF have any issues with NUMA memory nodes? It can just ignore 
>> them, no?
> 
> Because the only way SLOF knows about the RMA is by using the first
> "reg" entry of the first memory node and that's *all* SLOF knows about.
> 
> If we start putting things like the DT, SLOF itself, etc... outside of
> that region, it will crash.
> 
> So we "constrain" things to the rma that way.
> 
> Creating 4M nodes makes no sense anyway

So why don't we just use the "limit VRMA to 256MB" code always and error out of 
node0 is smaller? I don't think SLOF can run with less than 256MB anyway.


Alex