Re: [PATCH v3 7/7] spapr_numa: use spapr_numa_get_vcpu_assoc() in home_node hcall

[David Gibson]

On Thu, Sep 03, 2020 at 07:06:39PM -0300, Daniel Henrique Barboza wrote:
> The current implementation of h_home_node_associativity hard codes
> the values of associativity domains of the vcpus. Let's make
> it consider the values already initialized in spapr->numa_assoc_array,
> via the spapr_numa_get_vcpu_assoc() helper.
> 
> We want to set it and forget it, and for that we also need to
> assert that we don't overflow the registers of the hypercall.
> >From R4 to R9 we can squeeze in 12 associativity domains, so
> let's assert that MAX_DISTANCE_REF_POINTS isn't greater
> than that.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  hw/ppc/spapr_numa.c | 33 +++++++++++++++++++++++++--------
>  1 file changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> index abc7361921..850e61bf98 100644
> --- a/hw/ppc/spapr_numa.c
> +++ b/hw/ppc/spapr_numa.c
> @@ -185,10 +185,12 @@ target_ulong h_home_node_associativity(PowerPCCPU *cpu,
>                                         target_ulong opcode,
>                                         target_ulong *args)
>  {
> +    g_autofree uint32_t *vcpu_assoc = NULL;
>      target_ulong flags = args[0];
>      target_ulong procno = args[1];
>      PowerPCCPU *tcpu;
> -    int idx;
> +    uint vcpu_assoc_size;
> +    int idx, assoc_idx;
>  
>      /* only support procno from H_REGISTER_VPA */
>      if (flags != 0x1) {
> @@ -200,16 +202,31 @@ target_ulong h_home_node_associativity(PowerPCCPU *cpu,
>          return H_P2;
>      }
>  
> -    /* sequence is the same as in the "ibm,associativity" property */
> +    /*
> +     * Given that we want to be flexible with the sizes and indexes,
> +     * we must consider that there is a hard limit of how many
> +     * associativities domain we can fit in R4 up to o R9, which
typo  ...............................................   ^

> +     * would be 12. Assert and bail if that's not the case.
> +     */
> +    g_assert(MAX_DISTANCE_REF_POINTS <= 12);

Since MAX_DISTANCE_REF_POINTS is a compile time constant, you could
use G_STATIC_ASSERT() to make this a compile rather than runtime
error.

> +
> +    vcpu_assoc = spapr_numa_get_vcpu_assoc(spapr, tcpu, &vcpu_assoc_size);
> +    vcpu_assoc_size /= sizeof(uint32_t);
> +    /* assoc_idx starts at 1 to skip associativity size */
> +    assoc_idx = 1;
>  
> -    idx = 0;
>  #define ASSOCIATIVITY(a, b) (((uint64_t)(a) << 32) | \
>                               ((uint64_t)(b) & 0xffffffff))
> -    args[idx++] = ASSOCIATIVITY(0, 0);
> -    args[idx++] = ASSOCIATIVITY(0, tcpu->node_id);
> -    args[idx++] = ASSOCIATIVITY(procno, -1);
> -    for ( ; idx < 6; idx++) {
> -        args[idx] = -1;
> +
> +    for (idx = 0; idx < 6; idx++) {
> +        int8_t a, b;

Do you really want int8_t, rather than say int32_t?

> +
> +        a = assoc_idx < vcpu_assoc_size ?
> +            be32_to_cpu(vcpu_assoc[assoc_idx++]) : -1;
> +        b = assoc_idx < vcpu_assoc_size ?
> +            be32_to_cpu(vcpu_assoc[assoc_idx++]) : -1;
> +
> +        args[idx] = ASSOCIATIVITY(a, b);
>      }
>  #undef ASSOCIATIVITY
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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