Re: [PATCH v5 2/3] spapr_numa: create a vcpu associativity helper

[Daniel Henrique Barboza <danielhb413@gmail.com>]

On 9/4/20 11:35 AM, Greg Kurz wrote:
> On Fri,  4 Sep 2020 10:56:30 -0300
> Daniel Henrique Barboza <danielhb413@gmail.com> wrote:
> 
>> The work to be done in h_home_node_associativity() intersects
>> with what is already done in spapr_numa_fixup_cpu_dt(). This
>> patch creates a new helper, spapr_numa_get_vcpu_assoc(), to
>> be used for both spapr_numa_fixup_cpu_dt() and
>> h_home_node_associativity().
>>
>> While we're at it, use memcpy() instead of loop assignment
>> to created the returned array.
>>
>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>> ---
>>   hw/ppc/spapr_numa.c    | 33 ++++++++++++++++++++-------------
>>   include/hw/ppc/spapr.h |  7 ++++++-
>>   2 files changed, 26 insertions(+), 14 deletions(-)
>>
>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>> index 368c1a494d..674d2ee86d 100644
>> --- a/hw/ppc/spapr_numa.c
>> +++ b/hw/ppc/spapr_numa.c
>> @@ -71,31 +71,38 @@ void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,
>>                         sizeof(spapr->numa_assoc_array[nodeid]))));
>>   }
>>   
>> -int spapr_numa_fixup_cpu_dt(SpaprMachineState *spapr, void *fdt,
>> -                            int offset, PowerPCCPU *cpu)
>> +static uint32_t *spapr_numa_get_vcpu_assoc(SpaprMachineState *spapr,
>> +                                           PowerPCCPU *cpu)
>>   {
>> -    uint vcpu_assoc_size = NUMA_ASSOC_SIZE + 1;
>> -    uint32_t vcpu_assoc[vcpu_assoc_size];
>> +    uint32_t *vcpu_assoc = g_malloc(VCPU_ASSOC_SIZE * sizeof(uint32_t));
> 
> CODING_STYLE recommends g_new(uint32_t, VCPU_ASSOC_SIZE)

Guess I can't rely solely on scripts/checkpath.pl anymore ....


> 
>>       int index = spapr_get_vcpu_id(cpu);
>> -    int i;
>> +
>> +    g_assert(vcpu_assoc != NULL);
>>   
> 
> g_malloc() and friends only return NULL when passed a zero size,
> which is obviously not the case here.

This was my attempt of trying to cover the case where g_malloc() might fail,
but reading the docs again I believe failure in g_malloc() would result in
application terminationl. What I did there makes sense for g_try_malloc().

I'll change up there for g_new() and drop this g_assert().



> 
>>       /*
>>        * VCPUs have an extra 'cpu_id' value in ibm,associativity
>>        * compared to other resources. Increment the size at index
>> -     * 0, copy all associativity domains already set, then put
>> -     * cpu_id last.
>> +     * 0, put cpu_id last, then copy the remaining associativity
>> +     * domains.
>>        */
>>       vcpu_assoc[0] = cpu_to_be32(MAX_DISTANCE_REF_POINTS + 1);
>> +    vcpu_assoc[VCPU_ASSOC_SIZE - 1] = cpu_to_be32(index);
>> +    memcpy(vcpu_assoc + 1, spapr->numa_assoc_array[cpu->node_id] + 1,
>> +           (VCPU_ASSOC_SIZE - 2) * sizeof(uint32_t));
>>   
>> -    for (i = 1; i <= MAX_DISTANCE_REF_POINTS; i++) {
>> -        vcpu_assoc[i] = spapr->numa_assoc_array[cpu->node_id][i];
>> -    }
>> +    return vcpu_assoc;
>> +}
>> +
>> +int spapr_numa_fixup_cpu_dt(SpaprMachineState *spapr, void *fdt,
>> +                            int offset, PowerPCCPU *cpu)
>> +{
>> +    g_autofree uint32_t *vcpu_assoc = NULL;
>>   
>> -    vcpu_assoc[vcpu_assoc_size - 1] = cpu_to_be32(index);
>> +    vcpu_assoc = spapr_numa_get_vcpu_assoc(spapr, cpu);
>>   
>>       /* Advertise NUMA via ibm,associativity */
>> -    return fdt_setprop(fdt, offset, "ibm,associativity",
>> -                       vcpu_assoc, sizeof(vcpu_assoc));
>> +    return fdt_setprop(fdt, offset, "ibm,associativity", vcpu_assoc,
>> +                       VCPU_ASSOC_SIZE * sizeof(uint32_t));
>>   }
>>   
>>   
>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>> index 9a63380801..e50a2672e3 100644
>> --- a/include/hw/ppc/spapr.h
>> +++ b/include/hw/ppc/spapr.h
>> @@ -107,13 +107,18 @@ typedef enum {
>>   
>>   /*
>>    * NUMA related macros. MAX_DISTANCE_REF_POINTS was taken
>> - * from Taken from Linux kernel arch/powerpc/mm/numa.h.
> 
> Heh a good opportunity to fix the "from Taken from" typo I guess ;)
> 
>> + * from Linux kernel arch/powerpc/mm/numa.h. It represents the
>> + * amount of associativity domains for non-CPU resources.
>>    *
>>    * NUMA_ASSOC_SIZE is the base array size of an ibm,associativity
>>    * array for any non-CPU resource.
>> + *
>> + * VCPU_ASSOC_SIZE represents the size of ibm,associativity array
>> + * for CPUs, which has an extra element (vcpu_id) in the end.
>>    */
>>   #define MAX_DISTANCE_REF_POINTS    4
>>   #define NUMA_ASSOC_SIZE            (MAX_DISTANCE_REF_POINTS + 1)
>> +#define VCPU_ASSOC_SIZE            (NUMA_ASSOC_SIZE + 1)
>>   
>>   typedef struct SpaprCapabilities SpaprCapabilities;
>>   struct SpaprCapabilities {
> 
> With the comments on g_malloc() addressed, feel free to add:
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>

Thanks! I'll change g_malloc() and so on like you suggested and send
this as v6.



DHB

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