Unverified Commit 789f3fa9 authored by Palmer Dabbelt's avatar Palmer Dabbelt
Browse files

Merge tag 'riscv-topo-on-6.0-rc1' of... 

Merge tag 'riscv-topo-on-6.0-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git/ into for-next

Fix RISC-V's topology reporting

The goal here is the fix the incorrectly reported arch topology on
RISC-V which seems to have been broken since it was added.
cpu, package and thread IDs are all currently reported as -1, so tools
like lstopo think systems have multiple threads on the same core when
this is not true:
https://github.com/open-mpi/hwloc/issues/536

arm64's topology code basically applies to RISC-V too, so it has been
made generic along with the removal of MPIDR related code, which
appears to be redudant code since '3102bc0e ("arm64: topology: Stop
using MPIDR for topology information")' replaced the code that actually
interacted with MPIDR with default values.

* tag 'riscv-topo-on-6.0-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git/:
  riscv: topology: fix default topology reporting
  arm64: topology: move store_cpu_topology() to shared code
parents 568035b0 fbd92809

arch/arm64/kernel/topology.c

+0 −40
Original line number Diff line number Diff line
@@ -22,46 +22,6 @@ 
#include <asm/cputype.h>

#include <asm/topology.h>



void store_cpu_topology(unsigned int cpuid)

{

	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];

	u64 mpidr;



	if (cpuid_topo->package_id != -1)

		goto topology_populated;



	mpidr = read_cpuid_mpidr();



	/* Uniprocessor systems can rely on default topology values */

	if (mpidr & MPIDR_UP_BITMASK)

		return;



	/*

	 * This would be the place to create cpu topology based on MPIDR.

	 *

	 * However, it cannot be trusted to depict the actual topology; some

	 * pieces of the architecture enforce an artificial cap on Aff0 values

	 * (e.g. GICv3's ICC_SGI1R_EL1 limits it to 15), leading to an

	 * artificial cycling of Aff1, Aff2 and Aff3 values. IOW, these end up

	 * having absolutely no relationship to the actual underlying system

	 * topology, and cannot be reasonably used as core / package ID.

	 *

	 * If the MT bit is set, Aff0 *could* be used to define a thread ID, but

	 * we still wouldn't be able to obtain a sane core ID. This means we

	 * need to entirely ignore MPIDR for any topology deduction.

	 */

	cpuid_topo->thread_id  = -1;

	cpuid_topo->core_id    = cpuid;

	cpuid_topo->package_id = cpu_to_node(cpuid);



	pr_debug("CPU%u: cluster %d core %d thread %d mpidr %#016llx\n",

		 cpuid, cpuid_topo->package_id, cpuid_topo->core_id,

		 cpuid_topo->thread_id, mpidr);



topology_populated:

	update_siblings_masks(cpuid);

}



#ifdef CONFIG_ACPI

static bool __init acpi_cpu_is_threaded(int cpu)

{

arch/riscv/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ config RISCV 
	select COMMON_CLK

	select CPU_PM if CPU_IDLE

	select EDAC_SUPPORT

	select GENERIC_ARCH_TOPOLOGY if SMP

	select GENERIC_ARCH_TOPOLOGY

	select GENERIC_ATOMIC64 if !64BIT

	select GENERIC_CLOCKEVENTS_BROADCAST if SMP

	select GENERIC_EARLY_IOREMAP

arch/riscv/kernel/smpboot.c

+2 −1
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus) 
	unsigned int curr_cpuid;



	curr_cpuid = smp_processor_id();

	store_cpu_topology(curr_cpuid);

	numa_store_cpu_info(curr_cpuid);

	numa_add_cpu(curr_cpuid);
@@ -162,9 +163,9 @@ asmlinkage __visible void smp_callin(void) 
	mmgrab(mm);

	current->active_mm = mm;



	store_cpu_topology(curr_cpuid);

	notify_cpu_starting(curr_cpuid);

	numa_add_cpu(curr_cpuid);

	update_siblings_masks(curr_cpuid);

	set_cpu_online(curr_cpuid, 1);



	/*

drivers/base/arch_topology.c

+19 −0
Original line number Diff line number Diff line
@@ -841,4 +841,23 @@ void __init init_cpu_topology(void) 
		return;

	}

}



void store_cpu_topology(unsigned int cpuid)

{

	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];



	if (cpuid_topo->package_id != -1)

		goto topology_populated;



	cpuid_topo->thread_id = -1;

	cpuid_topo->core_id = cpuid;

	cpuid_topo->package_id = cpu_to_node(cpuid);



	pr_debug("CPU%u: package %d core %d thread %d\n",

		 cpuid, cpuid_topo->package_id, cpuid_topo->core_id,

		 cpuid_topo->thread_id);



topology_populated:

	update_siblings_masks(cpuid);

}

#endif