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SubjectRe: [patch V2 30/67] powerpc/numa: Convert to hotplug state machine
Hi,

> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> Install the callbacks via the state machine and let the core invoke
> the callbacks on the already online CPUs.

This is causing an oops on ppc64le QEMU, looks like a NULL pointer:

percpu: Embedded 3 pages/cpu @c00000001fe00000 s145816 r0 d50792 u1048576
Unable to handle kernel paging request for data at address 0x00001e08
Faulting instruction address: 0xc0000000001e6b78
Oops: Kernel access of bad area, sig: 11 [#1]
SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 4.7.0-rc7-00198-g425209e #14
task: c000000000d82a00 ti: c000000000dc4000 task.ti: c000000000dc4000
NIP: c0000000001e6b78 LR: c0000000001e6df4 CTR: 0000000000000000
REGS: c000000000dc7b60 TRAP: 0300 Not tainted (4.7.0-rc7-00198-g425209e)
MSR: 8000000002001033 <SF,VEC,ME,IR,DR,RI,LE> CR: 44000220 XER: 00000000
CFAR: 0000000000008468 DAR: 0000000000001e08 DSISR: 40000000 SOFTE: 0
GPR00: 0000000000000006 c000000000dc7de0 c000000000dc6c00 0000000000000000
GPR04: 0000000000000000 0000000000000000 c00000001fe1fb70 0000000000000010
GPR08: c000000000dfe918 c000000000e50dd0 c000000000e56c00 0000000000000001
GPR12: 0000000000000000 c00000000fe00000 0000000000000060 0000000000f1d618
GPR16: 0000000000efccd8 0000000000efcb20 fffffffffffffffd 0000000000000000
GPR20: 000000001f150000 c000000000dfa8e0 c000000000ccfafc c000000000dfeb18
GPR24: c000000000dfee34 c000000000ccfaf8 0000000000000000 0000000000000001
GPR28: c000000000ebad20 c000000000ccfb00 0000000000000000 c00000001fe1fb00
NIP [c0000000001e6b78] local_memory_node+0x18/0x80
LR [c0000000001e6df4] __build_all_zonelists+0x214/0x2d0
Call Trace:
[c000000000dc7de0] [c0000000001e6ccc] __build_all_zonelists+0xec/0x2d0 (unreliable)
[c000000000dc7e70] [c000000000c39fbc] build_all_zonelists_init+0x1c/0x3c
[c000000000dc7e90] [c000000000282acc] build_all_zonelists+0x17c/0x18c
[c000000000dc7f00] [c000000000c13c54] start_kernel+0x18c/0x514
[c000000000dc7f90] [c000000000008c60] start_here_common+0x20/0xa0
Instruction dump:
38810178 7f63db78 48769171 60000000 4bfffd2c 60420000 3c4c00be 384200a0
3d420009 78631f24 392aa1d0 7c69182a <81231e08> 38631e00 2b890002 419d001c

Anton

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Cc: Christophe Jaillet <christophe.jaillet@wanadoo.fr>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> ---
> arch/powerpc/mm/numa.c | 46
> ++++++++++++++++------------------------------
> include/linux/cpuhotplug.h | 1 + 2 files changed, 17 insertions(+),
> 30 deletions(-)
>
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 669a15e..d48ac48 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -581,30 +581,22 @@ static void verify_cpu_node_mapping(int cpu,
> int node) }
> }
>
> -static int cpu_numa_callback(struct notifier_block *nfb, unsigned
> long action,
> - void *hcpu)
> +/* Must run before sched domains notifier. */
> +static int ppc_numa_cpu_prepare(unsigned int cpu)
> {
> - unsigned long lcpu = (unsigned long)hcpu;
> - int ret = NOTIFY_DONE, nid;
> + int nid;
>
> - switch (action) {
> - case CPU_UP_PREPARE:
> - case CPU_UP_PREPARE_FROZEN:
> - nid = numa_setup_cpu(lcpu);
> - verify_cpu_node_mapping((int)lcpu, nid);
> - ret = NOTIFY_OK;
> - break;
> + nid = numa_setup_cpu(cpu);
> + verify_cpu_node_mapping(cpu, nid);
> + return 0;
> +}
> +
> +static int ppc_numa_cpu_dead(unsigned int cpu)
> +{
> #ifdef CONFIG_HOTPLUG_CPU
> - case CPU_DEAD:
> - case CPU_DEAD_FROZEN:
> - case CPU_UP_CANCELED:
> - case CPU_UP_CANCELED_FROZEN:
> - unmap_cpu_from_node(lcpu);
> - ret = NOTIFY_OK;
> - break;
> + unmap_cpu_from_node(cpu);
> #endif
> - }
> - return ret;
> + return 0;
> }
>
> /*
> @@ -913,11 +905,6 @@ static void __init
> dump_numa_memory_topology(void) }
> }
>
> -static struct notifier_block ppc64_numa_nb = {
> - .notifier_call = cpu_numa_callback,
> - .priority = 1 /* Must run before sched domains notifier. */
> -};
> -
> /* Initialize NODE_DATA for a node on the local memory */
> static void __init setup_node_data(int nid, u64 start_pfn, u64
> end_pfn) {
> @@ -953,7 +940,7 @@ static void __init setup_node_data(int nid, u64
> start_pfn, u64 end_pfn)
> void __init initmem_init(void)
> {
> - int nid, cpu;
> + int nid;
>
> max_low_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
> max_pfn = max_low_pfn;
> @@ -985,15 +972,14 @@ void __init initmem_init(void)
> setup_node_to_cpumask_map();
>
> reset_numa_cpu_lookup_table();
> - register_cpu_notifier(&ppc64_numa_nb);
> +
> /*
> * We need the numa_cpu_lookup_table to be accurate for all
> CPUs,
> * even before we online them, so that we can use
> cpu_to_{node,mem}
> * early in boot, cf. smp_prepare_cpus().
> */
> - for_each_present_cpu(cpu) {
> - numa_setup_cpu((unsigned long)cpu);
> - }
> + cpuhp_setup_state(CPUHP_POWER_NUMA_PREPARE,
> "POWER_NUMA_PREPARE",
> + ppc_numa_cpu_prepare, ppc_numa_cpu_dead);
> }
>
> static int __init early_numa(char *p)
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 7449081..01133ec 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -14,6 +14,7 @@ enum cpuhp_state {
> CPUHP_PERF_SUPERH,
> CPUHP_X86_HPET_DEAD,
> CPUHP_WORKQUEUE_PREP,
> + CPUHP_POWER_NUMA_PREPARE,
> CPUHP_NOTIFY_PREPARE,
> CPUHP_BRINGUP_CPU,
> CPUHP_AP_IDLE_DEAD,

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