Re: [for-5.0 3/4] spapr: Clean up RMA size calculation

[Alexey Kardashevskiy]

On 03/12/2019 14:44, Alexey Kardashevskiy wrote:
> 
> 
> On 29/11/2019 12:35, David Gibson wrote:
>> Move the calculation of the Real Mode Area (RMA) size into a helper
>> function.  While we're there clean it up and correct it in a few ways:
>>   * Add comments making it clearer where the various constraints come from
>>   * Remove a pointless check that the RMA fits within Node 0 (we've just
>>     clamped it so that it does)
>>   * The 16GiB limit we apply is only correct for POWER8, but there is also
>>     a 1TiB limit that applies on POWER9.
>>
>> Signed-off-by: David Gibson <address@hidden>
>> ---
>>  hw/ppc/spapr.c | 57 +++++++++++++++++++++++++++++++-------------------
>>  1 file changed, 35 insertions(+), 22 deletions(-)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index 52c39daa99..7efd4f2b85 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -2664,6 +2664,40 @@ static PCIHostState *spapr_create_default_phb(void)
>>      return PCI_HOST_BRIDGE(dev);
>>  }
>>  
>> +static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
>> +{
>> +    MachineState *machine = MACHINE(spapr);
>> +    hwaddr rma_size = machine->ram_size;
>> +    hwaddr node0_size = spapr_node0_size(machine);
>> +
>> +    /* RMA has to fit in the first NUMA node */
>> +    rma_size = MIN(rma_size, node0_size);
>> +
>> +    /*
>> +     * VRMA access is via a special 1TiB SLB mapping, so the RMA can
>> +     * never exceed that
>> +     */
>> +    rma_size = MIN(rma_size, TiB);
>> +
>> +    /*
>> +     * RMA size is controlled in hardware by LPCR[RMLS].  On POWER8
> 
> 
> RMA is controlled by LPCR on P8 but the RMLS bits on P9 are reserved
> (also reserved in PowerISA 3.0).
> 
> 
>> +     * the largest RMA that can be specified there is 16GiB
> 
> 
> The P8 user manual says:
> ===
> The following RMO sizes are available for the POWER8 processor.
> The RMLS[34:37] field in the LPCR defines the RMO sizes, as described below.
> 1000 - 32 MB
> 0011 - 64 MB
> 0111 - 128 MB
> 0100 - 256 MB
> 0010 - 1 GB
> 0001 - 16 GB
> 0000 - 256 GB
> ===
> 
> The maximum seems to be 256GiB.


Ah, update from Paul - we do not actually use what LPCR[RMLS] controls -
Real Mode Offset Register (RMOR).



> 
> 
>> +     */
>> +    if (!ppc_type_check_compat(machine->cpu_type, CPU_POWERPC_LOGICAL_3_00,
>> +                               0, spapr->max_compat_pvr)) {
>> +        rma_size = MIN(rma_size, 16 * GiB);
>> +    }
>> +
>> +    if (rma_size < (MIN_RMA_SLOF * MiB)) {
> 
> 
> nit: it is time to redefine MIN_RMA_SLOF to use MiBs imho :)
> 
> 
>> +        error_setg(errp,
>> +"pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area)",
>> +                   MIN_RMA_SLOF);
> 
> Something went wrong with formatting here.
> 
> Otherwise looks good. Thanks,
> 
> 
> 
>> +        return -1;
>> +    }
>> +
>> +    return rma_size;
>> +}
>> +
>>  /* pSeries LPAR / sPAPR hardware init */
>>  static void spapr_machine_init(MachineState *machine)
>>  {
>> @@ -2675,7 +2709,6 @@ static void spapr_machine_init(MachineState *machine)
>>      int i;
>>      MemoryRegion *sysmem = get_system_memory();
>>      MemoryRegion *ram = g_new(MemoryRegion, 1);
>> -    hwaddr node0_size = spapr_node0_size(machine);
>>      long load_limit, fw_size;
>>      char *filename;
>>      Error *resize_hpt_err = NULL;
>> @@ -2715,20 +2748,7 @@ static void spapr_machine_init(MachineState *machine)
>>          exit(1);
>>      }
>>  
>> -    spapr->rma_size = node0_size;
>> -
>> -    /* Actually we don't support unbounded RMA anymore since we added
>> -     * proper emulation of HV mode. The max we can get is 16G which
>> -     * also happens to be what we configure for PAPR mode so make sure
>> -     * we don't do anything bigger than that
>> -     */
>> -    spapr->rma_size = MIN(spapr->rma_size, 0x400000000ull);
>> -
>> -    if (spapr->rma_size > node0_size) {
>> -        error_report("Numa node 0 has to span the RMA (%#08"HWADDR_PRIx")",
>> -                     spapr->rma_size);
>> -        exit(1);
>> -    }
>> +    spapr->rma_size = spapr_rma_size(spapr, &error_fatal);
>>  
>>      /* Setup a load limit for the ramdisk leaving room for SLOF and FDT */
>>      load_limit = MIN(spapr->rma_size, RTAS_MAX_ADDR) - FW_OVERHEAD;
>> @@ -2956,13 +2976,6 @@ static void spapr_machine_init(MachineState *machine)
>>          }
>>      }
>>  
>> -    if (spapr->rma_size < (MIN_RMA_SLOF * MiB)) {
>> -        error_report(
>> -            "pSeries SLOF firmware requires >= %ldM guest RMA (Real Mode 
>> Area memory)",
>> -            MIN_RMA_SLOF);
>> -        exit(1);
>> -    }
>> -
>>      if (kernel_filename) {
>>          uint64_t lowaddr = 0;
>>  
>>
> 

-- 
Alexey