Re: [PATCH] arch_topology: Make cluster topology span at least SMT CPUs

Sudeep Holla
2022-08-23T11:27:45Z

On Tue, Aug 23, 2022 at 03:30:44PM +0800, Yicong Yang wrote:
> From: Yicong Yang <yangyicong@hisilicon.com>
>
> Currently cpu_clustergroup_mask() will return CPU mask if cluster span
> more or the same CPUs as cpu_coregroup_mask(). This will result topology
> borken on non-Cluster SMT machines.
>
> Test with:
> qemu-system-aarch64 -enable-kvm -machine virt \
> -net none \
> -cpu host \
> -bios ./QEMU_EFI.fd \
> -m 2G \
> -smp 48,sockets=2,cores=12,threads=2 \
> -kernel $Image \
> -initrd $Rootfs \
> -nographic
> -append "rdinit=init console=ttyAMA0 sched_verbose loglevel=8"
>
> We'll get below error:
> [ 3.084568] BUG: arch topology borken
> [ 3.084570] the SMT domain not a subset of the CLS domain
>
> Since cluster is a level higher than SMT, fix this by making cluster
> spans at least SMT CPUs.
>
> Cc: Sudeep Holla <sudeep.holla@arm.com>

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Ionela Voinescu <ionela.voinescu@arm.com>
> Fixes: bfcc4397435d ("arch_topology: Limit span of cpu_clustergroup_mask()")
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> ---
> drivers/base/arch_topology.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 0424b59b695e..0056a1273275 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -724,7 +724,7 @@ const struct cpumask *cpu_clustergroup_mask(int cpu)
> */
> if (cpumask_subset(cpu_coregroup_mask(cpu),
> &cpu_topology[cpu].cluster_sibling))
> - return get_cpu_mask(cpu);

Sorry for this, for some reason I assumed the get_cpu_mask() will cover
threads too.

--
Regards,
Sudeep