[PATCH v3 0/5] Updates to powerpc for robust CPU online/offline

[PATCH v3 0/5] Updates to powerpc for robust CPU online/offline

[Srikar Dronamraju]

Changelog v2 -> v3:
v2: https://lore.kernel.org/linuxppc-dev/20210821102535.169643-1-srikar@linux.vnet.ibm.com/t/#u
Add patch 1: to drop dbg and numa=debug (Suggested by Michael Ellerman)
Add patch 2: to convert printk to pr_xxx (Suggested by Michael Ellerman)
	Use pr_warn instead of pr_debug(WARNING) (Suggested by Laurent)

Changelog v1 -> v2:
Moved patch to this series: powerpc/numa: Fill distance_lookup_table for offline nodes
fixed a missing prototype warning

Scheduler expects unique number of node distances to be available
at boot. It uses node distance to calculate this unique node
distances. On Power Servers, node distances for offline nodes is not
available. However, Power Servers already knows unique possible node
distances. Fake the offline node's distance_lookup_table entries so
that all possible node distances are updated.

For example distance info from numactl from a fully populated 8 node
system at boot may look like this.

node distances:
node   0   1   2   3   4   5   6   7
  0:  10  20  40  40  40  40  40  40
  1:  20  10  40  40  40  40  40  40
  2:  40  40  10  20  40  40  40  40
  3:  40  40  20  10  40  40  40  40
  4:  40  40  40  40  10  20  40  40
  5:  40  40  40  40  20  10  40  40
  6:  40  40  40  40  40  40  10  20
  7:  40  40  40  40  40  40  20  10

However the same system when only two nodes are online at boot, then
distance info from numactl will look like
node distances:
node   0   1
  0:  10  20
  1:  20  10

With the faked numa distance at boot, the node distance table will look
like
node   0   1   2
  0:  10  20  40
  1:  20  10  40
  2:  40  40  10

The actual distance will be populated once the nodes are onlined.

Also when simultaneously running CPU online/offline with CPU
add/remove in a loop, we see a WARNING messages.

WARNING: CPU: 13 PID: 1142 at kernel/sched/topology.c:898 build_sched_domains+0xd48/0x1720
Modules linked in: rpadlpar_io rpaphp mptcp_diag xsk_diag tcp_diag udp_diag
raw_diag inet_diag unix_diag af_packet_diag netlink_diag bonding tls
nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet
nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat
nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set rfkill nf_tables nfnetlink
pseries_rng xts vmx_crypto uio_pdrv_genirq uio binfmt_misc ip_tables xfs
libcrc32c dm_service_time sd_mod t10_pi sg ibmvfc scsi_transport_fc ibmveth
dm_multipath dm_mirror dm_region_hash dm_log dm_mod fuse
CPU: 13 PID: 1142 Comm: kworker/13:2 Not tainted 5.13.0-rc6+ #28
Workqueue: events cpuset_hotplug_workfn
NIP:  c0000000001caac8 LR: c0000000001caac4 CTR: 00000000007088ec
REGS: c00000005596f220 TRAP: 0700   Not tainted  (5.13.0-rc6+)
MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 48828222  XER: 00000009
CFAR: c0000000001ea698 IRQMASK: 0
GPR00: c0000000001caac4 c00000005596f4c0 c000000001c4a400 0000000000000036
GPR04: 00000000fffdffff c00000005596f1d0 0000000000000027 c0000018cfd07f90
GPR08: 0000000000000023 0000000000000001 0000000000000027 c0000018fe68ffe8
GPR12: 0000000000008000 c00000001e9d1880 c00000013a047200 0000000000000800
GPR16: c000000001d3c7d0 0000000000000240 0000000000000048 c000000010aacd18
GPR20: 0000000000000001 c000000010aacc18 c00000013a047c00 c000000139ec2400
GPR24: 0000000000000280 c000000139ec2520 c000000136c1b400 c000000001c93060
GPR28: c00000013a047c20 c000000001d3c6c0 c000000001c978a0 000000000000000d
NIP [c0000000001caac8] build_sched_domains+0xd48/0x1720
LR [c0000000001caac4] build_sched_domains+0xd44/0x1720
Call Trace:
[c00000005596f4c0] [c0000000001caac4] build_sched_domains+0xd44/0x1720 (unreliable)
[c00000005596f670] [c0000000001cc5ec] partition_sched_domains_locked+0x3ac/0x4b0
[c00000005596f710] [c0000000002804e4] rebuild_sched_domains_locked+0x404/0x9e0
[c00000005596f810] [c000000000283e60] rebuild_sched_domains+0x40/0x70
[c00000005596f840] [c000000000284124] cpuset_hotplug_workfn+0x294/0xf10
[c00000005596fc60] [c000000000175040] process_one_work+0x290/0x590
[c00000005596fd00] [c0000000001753c8] worker_thread+0x88/0x620
[c00000005596fda0] [c000000000181704] kthread+0x194/0x1a0
[c00000005596fe10] [c00000000000ccec] ret_from_kernel_thread+0x5c/0x70
Instruction dump:
485af049 60000000 2fa30800 409e0028 80fe0000 e89a00f8 e86100e8 38da0120
7f88e378 7ce53b78 4801fb91 60000000 <0fe00000> 39000000 38e00000 38c00000

This was because cpu_cpu_mask() was not getting updated on CPU
online/offline but would be only updated when add/remove of CPUs.
Other cpumasks get updated both on CPU online/offline and add/remove
Update cpu_cpu_mask() on CPU online/offline too.

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>

Srikar Dronamraju (5):
  powerpc/numa: Drop dbg in favour of pr_debug
  powerpc/numa: convert printk to pr_xxx
  powerpc/numa: Print debug statements only when required
  powerpc/numa: Update cpu_cpu_map on CPU online/offline
  powerpc/numa: Fill distance_lookup_table for offline nodes

 arch/powerpc/include/asm/topology.h |  12 +++
 arch/powerpc/kernel/smp.c           |   3 +
 arch/powerpc/mm/numa.c              | 120 ++++++++++++++++++++--------
 3 files changed, 103 insertions(+), 32 deletions(-)

-- 
2.18.2

[PATCH v5 1/5] powerpc/numa: Drop dbg in favour of pr_debug

[Srikar Dronamraju]

PowerPc supported numa=debug which is not documented. This option was
used to print early debug output. However something more flexible can be
achieved by using CONFIG_DYNAMIC_DEBUG.

Hence drop dbg (and numa=debug) in favour of pr_debug

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index f2bf98bdcea2..5e9b777a1151 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -40,9 +40,6 @@ static int numa_enabled = 1;
 
 static char *cmdline __initdata;
 
-static int numa_debug;
-#define dbg(args...) if (numa_debug) { printk(KERN_INFO args); }
-
 int numa_cpu_lookup_table[NR_CPUS];
 cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
 struct pglist_data *node_data[MAX_NUMNODES];
@@ -79,7 +76,7 @@ static void __init setup_node_to_cpumask_map(void)
 		alloc_bootmem_cpumask_var(&node_to_cpumask_map[node]);
 
 	/* cpumask_of_node() will now work */
-	dbg("Node to cpumask map for %u nodes\n", nr_node_ids);
+	pr_debug("Node to cpumask map for %u nodes\n", nr_node_ids);
 }
 
 static int __init fake_numa_create_new_node(unsigned long end_pfn,
@@ -123,7 +120,7 @@ static int __init fake_numa_create_new_node(unsigned long end_pfn,
 		cmdline = p;
 		fake_nid++;
 		*nid = fake_nid;
-		dbg("created new fake_node with id %d\n", fake_nid);
+		pr_debug("created new fake_node with id %d\n", fake_nid);
 		return 1;
 	}
 	return 0;
@@ -141,7 +138,7 @@ static void map_cpu_to_node(int cpu, int node)
 {
 	update_numa_cpu_lookup_table(cpu, node);
 
-	dbg("adding cpu %d to node %d\n", cpu, node);
+	pr_debug("adding cpu %d to node %d\n", cpu, node);
 
 	if (!(cpumask_test_cpu(cpu, node_to_cpumask_map[node])))
 		cpumask_set_cpu(cpu, node_to_cpumask_map[node]);
@@ -152,7 +149,7 @@ static void unmap_cpu_from_node(unsigned long cpu)
 {
 	int node = numa_cpu_lookup_table[cpu];
 
-	dbg("removing cpu %lu from node %d\n", cpu, node);
+	pr_debug("removing cpu %lu from node %d\n", cpu, node);
 
 	if (cpumask_test_cpu(cpu, node_to_cpumask_map[node])) {
 		cpumask_clear_cpu(cpu, node_to_cpumask_map[node]);
@@ -313,7 +310,7 @@ static int __init find_min_common_depth(void)
 					&distance_ref_points_depth);
 
 	if (!distance_ref_points) {
-		dbg("NUMA: ibm,associativity-reference-points not found.\n");
+		pr_debug("NUMA: ibm,associativity-reference-points not found.\n");
 		goto err;
 	}
 
@@ -321,7 +318,7 @@ static int __init find_min_common_depth(void)
 
 	if (firmware_has_feature(FW_FEATURE_OPAL) ||
 	    firmware_has_feature(FW_FEATURE_TYPE1_AFFINITY)) {
-		dbg("Using form 1 affinity\n");
+		pr_debug("Using form 1 affinity\n");
 		form1_affinity = 1;
 	}
 
@@ -719,7 +716,7 @@ static int __init parse_numa_properties(void)
 		return min_common_depth;
 	}
 
-	dbg("NUMA associativity depth for CPU/Memory: %d\n", min_common_depth);
+	pr_debug("NUMA associativity depth for CPU/Memory: %d\n", min_common_depth);
 
 	/*
 	 * Even though we connect cpus to numa domains later in SMP
@@ -1014,9 +1011,6 @@ static int __init early_numa(char *p)
 	if (strstr(p, "off"))
 		numa_enabled = 0;
 
-	if (strstr(p, "debug"))
-		numa_debug = 1;
-
 	p = strstr(p, "fake=");
 	if (p)
 		cmdline = p + strlen("fake=");
@@ -1179,7 +1173,7 @@ static long vphn_get_associativity(unsigned long cpu,
 
 	switch (rc) {
 	case H_SUCCESS:
-		dbg("VPHN hcall succeeded. Reset polling...\n");
+		pr_debug("VPHN hcall succeeded. Reset polling...\n");
 		goto out;
 
 	case H_FUNCTION:
-- 
2.18.2

[PATCH v5 2/5] powerpc/numa: convert printk to pr_xxx

[Srikar Dronamraju]

Convert the remaining printk to pr_xxx
One advantage would be all prints will now have prefix "numa:" from
pr_fmt().

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
[ convert printk(KERN_ERR) to pr_warn : Suggested by Laurent Dufour ]
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5e9b777a1151..9af38b1c618b 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -154,8 +154,7 @@ static void unmap_cpu_from_node(unsigned long cpu)
 	if (cpumask_test_cpu(cpu, node_to_cpumask_map[node])) {
 		cpumask_clear_cpu(cpu, node_to_cpumask_map[node]);
 	} else {
-		printk(KERN_ERR "WARNING: cpu %lu not found in node %d\n",
-		       cpu, node);
+		pr_warn("WARNING: cpu %lu not found in node %d\n", cpu, node);
 	}
 }
 #endif /* CONFIG_HOTPLUG_CPU || CONFIG_PPC_SPLPAR */
@@ -326,8 +325,7 @@ static int __init find_min_common_depth(void)
 		depth = of_read_number(distance_ref_points, 1);
 	} else {
 		if (distance_ref_points_depth < 2) {
-			printk(KERN_WARNING "NUMA: "
-				"short ibm,associativity-reference-points\n");
+			pr_warn("short ibm,associativity-reference-points\n");
 			goto err;
 		}
 
@@ -339,7 +337,7 @@ static int __init find_min_common_depth(void)
 	 * MAX_DISTANCE_REF_POINTS domains.
 	 */
 	if (distance_ref_points_depth > MAX_DISTANCE_REF_POINTS) {
-		printk(KERN_WARNING "NUMA: distance array capped at "
+		pr_warn("distance array capped at "
 			"%d entries\n", MAX_DISTANCE_REF_POINTS);
 		distance_ref_points_depth = MAX_DISTANCE_REF_POINTS;
 	}
@@ -701,7 +699,7 @@ static int __init parse_numa_properties(void)
 	unsigned long i;
 
 	if (numa_enabled == 0) {
-		printk(KERN_WARNING "NUMA disabled by user\n");
+		pr_warn("disabled by user\n");
 		return -1;
 	}
 
@@ -716,7 +714,7 @@ static int __init parse_numa_properties(void)
 		return min_common_depth;
 	}
 
-	pr_debug("NUMA associativity depth for CPU/Memory: %d\n", min_common_depth);
+	pr_debug("associativity depth for CPU/Memory: %d\n", min_common_depth);
 
 	/*
 	 * Even though we connect cpus to numa domains later in SMP
@@ -808,10 +806,8 @@ static void __init setup_nonnuma(void)
 	unsigned int nid = 0;
 	int i;
 
-	printk(KERN_DEBUG "Top of RAM: 0x%lx, Total RAM: 0x%lx\n",
-	       top_of_ram, total_ram);
-	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
-	       (top_of_ram - total_ram) >> 20);
+	pr_debug("Top of RAM: 0x%lx, Total RAM: 0x%lx\n", top_of_ram, total_ram);
+	pr_debug("Memory hole size: %ldMB\n", (top_of_ram - total_ram) >> 20);
 
 	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
 		fake_numa_create_new_node(end_pfn, &nid);
-- 
2.18.2

[PATCH v3 3/5] powerpc/numa: Print debug statements only when required

[Srikar Dronamraju]

Currently, a debug message gets printed every time an attempt to
add(remove) a CPU. However this is redundant if the CPU is already added
(removed) from the node.

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 9af38b1c618b..6655ecdeddef 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -138,10 +138,10 @@ static void map_cpu_to_node(int cpu, int node)
 {
 	update_numa_cpu_lookup_table(cpu, node);
 
-	pr_debug("adding cpu %d to node %d\n", cpu, node);
-
-	if (!(cpumask_test_cpu(cpu, node_to_cpumask_map[node])))
+	if (!(cpumask_test_cpu(cpu, node_to_cpumask_map[node]))) {
+		pr_debug("adding cpu %d to node %d\n", cpu, node);
 		cpumask_set_cpu(cpu, node_to_cpumask_map[node]);
+	}
 }
 
 #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PPC_SPLPAR)
@@ -149,10 +149,9 @@ static void unmap_cpu_from_node(unsigned long cpu)
 {
 	int node = numa_cpu_lookup_table[cpu];
 
-	pr_debug("removing cpu %lu from node %d\n", cpu, node);
-
 	if (cpumask_test_cpu(cpu, node_to_cpumask_map[node])) {
 		cpumask_clear_cpu(cpu, node_to_cpumask_map[node]);
+		pr_debug("removing cpu %lu from node %d\n", cpu, node);
 	} else {
 		pr_warn("WARNING: cpu %lu not found in node %d\n", cpu, node);
 	}
-- 
2.18.2

[PATCH v3 4/5] powerpc/numa: Update cpu_cpu_map on CPU online/offline

[Srikar Dronamraju]

cpu_cpu_map holds all the CPUs in the DIE. However in PowerPC, when
onlining/offlining of CPUs, this mask doesn't get updated.  This mask
is however updated when CPUs are added/removed. So when both
operations like online/offline of CPUs and adding/removing of CPUs are
done simultaneously, then cpumaps end up broken.

WARNING: CPU: 13 PID: 1142 at kernel/sched/topology.c:898
build_sched_domains+0xd48/0x1720
Modules linked in: rpadlpar_io rpaphp mptcp_diag xsk_diag tcp_diag
udp_diag raw_diag inet_diag unix_diag af_packet_diag netlink_diag
bonding tls nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib
nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct
nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set
rfkill nf_tables nfnetlink pseries_rng xts vmx_crypto uio_pdrv_genirq
uio binfmt_misc ip_tables xfs libcrc32c dm_service_time sd_mod t10_pi sg
ibmvfc scsi_transport_fc ibmveth dm_multipath dm_mirror dm_region_hash
dm_log dm_mod fuse
CPU: 13 PID: 1142 Comm: kworker/13:2 Not tainted 5.13.0-rc6+ #28
Workqueue: events cpuset_hotplug_workfn
NIP:  c0000000001caac8 LR: c0000000001caac4 CTR: 00000000007088ec
REGS: c00000005596f220 TRAP: 0700   Not tainted  (5.13.0-rc6+)
MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 48828222  XER:
00000009
CFAR: c0000000001ea698 IRQMASK: 0
GPR00: c0000000001caac4 c00000005596f4c0 c000000001c4a400 0000000000000036
GPR04: 00000000fffdffff c00000005596f1d0 0000000000000027 c0000018cfd07f90
GPR08: 0000000000000023 0000000000000001 0000000000000027 c0000018fe68ffe8
GPR12: 0000000000008000 c00000001e9d1880 c00000013a047200 0000000000000800
GPR16: c000000001d3c7d0 0000000000000240 0000000000000048 c000000010aacd18
GPR20: 0000000000000001 c000000010aacc18 c00000013a047c00 c000000139ec2400
GPR24: 0000000000000280 c000000139ec2520 c000000136c1b400 c000000001c93060
GPR28: c00000013a047c20 c000000001d3c6c0 c000000001c978a0 000000000000000d
NIP [c0000000001caac8] build_sched_domains+0xd48/0x1720
LR [c0000000001caac4] build_sched_domains+0xd44/0x1720
Call Trace:
[c00000005596f4c0] [c0000000001caac4] build_sched_domains+0xd44/0x1720 (unreliable)
[c00000005596f670] [c0000000001cc5ec] partition_sched_domains_locked+0x3ac/0x4b0
[c00000005596f710] [c0000000002804e4] rebuild_sched_domains_locked+0x404/0x9e0
[c00000005596f810] [c000000000283e60] rebuild_sched_domains+0x40/0x70
[c00000005596f840] [c000000000284124] cpuset_hotplug_workfn+0x294/0xf10
[c00000005596fc60] [c000000000175040] process_one_work+0x290/0x590
[c00000005596fd00] [c0000000001753c8] worker_thread+0x88/0x620
[c00000005596fda0] [c000000000181704] kthread+0x194/0x1a0
[c00000005596fe10] [c00000000000ccec] ret_from_kernel_thread+0x5c/0x70
Instruction dump:
485af049 60000000 2fa30800 409e0028 80fe0000 e89a00f8 e86100e8 38da0120
7f88e378 7ce53b78 4801fb91 60000000 <0fe00000> 39000000 38e00000 38c00000

Fix this by updating cpu_cpu_map aka cpumask_of_node() on every CPU
online/offline.

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/topology.h | 12 ++++++++++++
 arch/powerpc/kernel/smp.c           |  3 +++
 arch/powerpc/mm/numa.c              |  7 ++-----
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index e4db64c0e184..2f0a4d7b95f6 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -65,6 +65,11 @@ static inline int early_cpu_to_node(int cpu)
 
 int of_drconf_to_nid_single(struct drmem_lmb *lmb);
 
+extern void map_cpu_to_node(int cpu, int node);
+#ifdef CONFIG_HOTPLUG_CPU
+extern void unmap_cpu_from_node(unsigned long cpu);
+#endif /* CONFIG_HOTPLUG_CPU */
+
 #else
 
 static inline int early_cpu_to_node(int cpu) { return 0; }
@@ -93,6 +98,13 @@ static inline int of_drconf_to_nid_single(struct drmem_lmb *lmb)
 	return first_online_node;
 }
 
+#ifdef CONFIG_SMP
+static inline void map_cpu_to_node(int cpu, int node) {}
+#ifdef CONFIG_HOTPLUG_CPU
+static inline void unmap_cpu_from_node(unsigned long cpu) {}
+#endif /* CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_SMP */
+
 #endif /* CONFIG_NUMA */
 
 #if defined(CONFIG_NUMA) && defined(CONFIG_PPC_SPLPAR)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index b31b8ca3ae2e..d947a4fd753c 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1407,6 +1407,8 @@ static void remove_cpu_from_masks(int cpu)
 	struct cpumask *(*mask_fn)(int) = cpu_sibling_mask;
 	int i;
 
+	unmap_cpu_from_node(cpu);
+
 	if (shared_caches)
 		mask_fn = cpu_l2_cache_mask;
 
@@ -1491,6 +1493,7 @@ static void add_cpu_to_masks(int cpu)
 	 * This CPU will not be in the online mask yet so we need to manually
 	 * add it to it's own thread sibling mask.
 	 */
+	map_cpu_to_node(cpu, cpu_to_node(cpu));
 	cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
 	cpumask_set_cpu(cpu, cpu_core_mask(cpu));
 
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 6655ecdeddef..87ade2f56f45 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -134,7 +134,7 @@ static void reset_numa_cpu_lookup_table(void)
 		numa_cpu_lookup_table[cpu] = -1;
 }
 
-static void map_cpu_to_node(int cpu, int node)
+void map_cpu_to_node(int cpu, int node)
 {
 	update_numa_cpu_lookup_table(cpu, node);
 
@@ -145,7 +145,7 @@ static void map_cpu_to_node(int cpu, int node)
 }
 
 #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PPC_SPLPAR)
-static void unmap_cpu_from_node(unsigned long cpu)
+void unmap_cpu_from_node(unsigned long cpu)
 {
 	int node = numa_cpu_lookup_table[cpu];
 
@@ -592,9 +592,6 @@ static int ppc_numa_cpu_prepare(unsigned int cpu)
 
 static int ppc_numa_cpu_dead(unsigned int cpu)
 {
-#ifdef CONFIG_HOTPLUG_CPU
-	unmap_cpu_from_node(cpu);
-#endif
 	return 0;
 }
 
-- 
2.18.2

[PATCH v3 5/5] powerpc/numa: Fill distance_lookup_table for offline nodes

[Srikar Dronamraju]

Scheduler expects unique number of node distances to be available at
boot. It uses node distance to calculate this unique node distances.
On POWER, node distances for offline nodes is not available. However,
POWER already knows unique possible node distances. Fake the offline
node's distance_lookup_table entries so that all possible node
distances are updated.

However this only needs to be done if the number of unique node
distances that can be computed for online nodes is less than the
number of possible unique node distances as represented by
distance_ref_points_depth. When the node is actually onlined,
distance_lookup_table will be updated with actual entries.

Cc: linuxppc-dev@lists.ozlabs.org
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c | 70 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

Changelog:
v1: https://lore.kernel.org/linuxppc-dev/20210701041552.112072-3-srikar@linux.vnet.ibm.com/t/#u
[ Fixed a missing prototype warning Reported-by: kernel test robot <lkp@intel.com>]

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 87ade2f56f45..afa2ede4ac53 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -849,6 +849,75 @@ void __init dump_numa_cpu_topology(void)
 	}
 }
 
+/*
+ * Scheduler expects unique number of node distances to be available at
+ * boot. It uses node distance to calculate this unique node distances. On
+ * POWER, node distances for offline nodes is not available. However, POWER
+ * already knows unique possible node distances. Fake the offline node's
+ * distance_lookup_table entries so that all possible node distances are
+ * updated.
+ */
+static void __init fake_update_distance_lookup_table(void)
+{
+	unsigned long distance_map;
+	int i, nr_levels, nr_depth, node;
+
+	if (!numa_enabled)
+		return;
+
+	if (!form1_affinity)
+		return;
+
+	/*
+	 * distance_ref_points_depth lists the unique numa domains
+	 * available. However it ignore LOCAL_DISTANCE. So add +1
+	 * to get the actual number of unique distances.
+	 */
+	nr_depth = distance_ref_points_depth + 1;
+
+	WARN_ON(nr_depth > sizeof(distance_map));
+
+	bitmap_zero(&distance_map, nr_depth);
+	bitmap_set(&distance_map, 0, 1);
+
+	for_each_online_node(node) {
+		int nd, distance = LOCAL_DISTANCE;
+
+		if (node == first_online_node)
+			continue;
+
+		nd = __node_distance(node, first_online_node);
+		for (i = 0; i < nr_depth; i++, distance *= 2) {
+			if (distance == nd) {
+				bitmap_set(&distance_map, i, 1);
+				break;
+			}
+		}
+		nr_levels = bitmap_weight(&distance_map, nr_depth);
+		if (nr_levels == nr_depth)
+			return;
+	}
+
+	for_each_node(node) {
+		if (node_online(node))
+			continue;
+
+		i = find_first_zero_bit(&distance_map, nr_depth);
+		if (i >= nr_depth || i == 0) {
+			pr_warn("Levels(%d) not matching levels(%d)", nr_levels, nr_depth);
+			return;
+		}
+
+		bitmap_set(&distance_map, i, 1);
+		while (i--)
+			distance_lookup_table[node][i] = node;
+
+		nr_levels = bitmap_weight(&distance_map, nr_depth);
+		if (nr_levels == nr_depth)
+			return;
+	}
+}
+
 /* Initialize NODE_DATA for a node on the local memory */
 static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
 {
@@ -964,6 +1033,7 @@ void __init mem_topology_setup(void)
 		 */
 		numa_setup_cpu(cpu);
 	}
+	fake_update_distance_lookup_table();
 }
 
 void __init initmem_init(void)
-- 
2.18.2

Re: [PATCH v3 0/5] Updates to powerpc for robust CPU online/offline

[Michael Ellerman]

On Thu, 26 Aug 2021 15:35:16 +0530, Srikar Dronamraju wrote:
> Changelog v2 -> v3:
> v2: https://lore.kernel.org/linuxppc-dev/20210821102535.169643-1-srikar@linux.vnet.ibm.com/t/#u
> Add patch 1: to drop dbg and numa=debug (Suggested by Michael Ellerman)
> Add patch 2: to convert printk to pr_xxx (Suggested by Michael Ellerman)
> 	Use pr_warn instead of pr_debug(WARNING) (Suggested by Laurent)
> 
> Changelog v1 -> v2:
> Moved patch to this series: powerpc/numa: Fill distance_lookup_table for offline nodes
> fixed a missing prototype warning
> 
> [...]

Patches 1-4 applied to powerpc/next.

[1/5] powerpc/numa: Drop dbg in favour of pr_debug
      https://git.kernel.org/powerpc/c/544af6429777cefae2f8af9a9866df5e8cb21763
[2/5] powerpc/numa: convert printk to pr_xxx
      https://git.kernel.org/powerpc/c/506c2075ffd8db352c53201ef166948a272e3bce
[3/5] powerpc/numa: Print debug statements only when required
      https://git.kernel.org/powerpc/c/544a09ee7434b949552266d20ece538d35535bd5
[4/5] powerpc/numa: Update cpu_cpu_map on CPU online/offline
      https://git.kernel.org/powerpc/c/9a245d0e1f006bc7ccf0285d0d520ed304d00c4a

cheers