On Thu, Jul 23, 2020 at 02:21:11PM +0530, Srikar Dronamraju wrote:
> Current code assumes that cpumask of cpus sharing a l2-cache mask will
> always be a superset of cpu_sibling_mask.
>
> Lets stop that assumption. cpu_l2_cache_mask is a superset of
> cpu_sibling_mask if and only if shared_caches is set.
>
> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
> Cc: LKML <linux-ker...@vger.kernel.org>
> Cc: Michael Ellerman <m...@ellerman.id.au>
> Cc: Nicholas Piggin <npig...@gmail.com>
> Cc: Anton Blanchard <an...@ozlabs.org>
> Cc: Oliver O'Halloran <ooh...@gmail.com>
> Cc: Nathan Lynch <nath...@linux.ibm.com>
> Cc: Michael Neuling <mi...@neuling.org>
> Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Valentin Schneider <valentin.schnei...@arm.com>
> Cc: Jordan Niethe <jniet...@gmail.com>
> Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
> ---
> Changelog v1 -> v2:
> Set cpumask after verifying l2-cache. (Gautham)
>
> arch/powerpc/kernel/smp.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index da27f6909be1..d997c7411664 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1194,6 +1194,7 @@ static bool update_mask_by_l2(int cpu, struct cpumask
> *(*mask_fn)(int))
> if (!l2_cache)
> return false;
>
> + cpumask_set_cpu(cpu, mask_fn(cpu));
> for_each_cpu(i, cpu_online_mask) {
> /*
> * when updating the marks the current CPU has not been marked
> @@ -1276,29 +1277,30 @@ static void add_cpu_to_masks(int cpu)
> * add it to it's own thread sibling mask.
> */
> cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> + cpumask_set_cpu(cpu, cpu_core_mask(cpu));
>
> for (i = first_thread; i < first_thread + threads_per_core; i++)
> if (cpu_online(i))
> set_cpus_related(i, cpu, cpu_sibling_mask);
>
> add_cpu_to_smallcore_masks(cpu);
> - /*
> - * Copy the thread sibling mask into the cache sibling mask
> - * and mark any CPUs that share an L2 with this CPU.
> - */
> - for_each_cpu(i, cpu_sibling_mask(cpu))
> - set_cpus_related(cpu, i, cpu_l2_cache_mask);
> update_mask_by_l2(cpu, cpu_l2_cache_mask);
>
> - /*
> - * Copy the cache sibling mask into core sibling mask and mark
> - * any CPUs on the same chip as this CPU.
> - */
> - for_each_cpu(i, cpu_l2_cache_mask(cpu))
> - set_cpus_related(cpu, i, cpu_core_mask);
> + if (pkg_id == -1) {
> + struct cpumask *(*mask)(int) = cpu_sibling_mask;
> +
> + /*
> + * Copy the sibling mask into core sibling mask and
> + * mark any CPUs on the same chip as this CPU.
> + */
> + if (shared_caches)
> + mask = cpu_l2_cache_mask;
> +
> + for_each_cpu(i, mask(cpu))
> + set_cpus_related(cpu, i, cpu_core_mask);
>
> - if (pkg_id == -1)
> return;
> + }
>
> for_each_cpu(i, cpu_online_mask)
> if (get_physical_package_id(i) == pkg_id)
> --
> 2.18.2
>
