[PATCHv4 2/3] powerpc, cpu: handling the special case when boot_cpuid greater than nr_cpus
From: Pingfan Liu <hidden>
Date: 2018-03-12 04:43:30
Also in:
kexec
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
For kexec -p, after boot_cpuid is mapping into the range of [0,
threads_per_core), then if nr_cpus is small, we will have the bitmap
[0,..., nr_cpus, ..., boot_cpuid, ...). This patch chooses cpus inside
the range of [boot_cpuid - nr_cpus +1, ..., boot_cpuid] to be online.
With this patch and the next, on a P9 machine with thread_per_core=4,
and set nr_cpus=2 for the crash kernel.
After
taskset -c 11 sh -c "echo c > /proc/sysrq-trigger"
Then
kdump:/sys/devices/system/cpu# cat possible
2-3
kdump:/sys/devices/system/cpu# cat present
2-3
kdump:/sys/devices/system/cpu# cat online
2-3
Signed-off-by: Pingfan Liu <redacted>
---
arch/powerpc/kernel/setup-common.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 1a67344..6920b5e 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c@@ -462,6 +462,8 @@ void __init smp_setup_cpu_maps(void) struct device_node *dn; struct device_node *boot_dn = NULL; bool handling_bootdn = true; + int head_thread = 0; + int online_cnt = 0; int cpu = 0; int nthreads = 1;
@@ -499,13 +501,19 @@ void __init smp_setup_cpu_maps(void) if (boot_cpuid < nthreads && be32_to_cpu(intserv[boot_cpuid]) == boot_cpuhwid) { boot_dn = dn; + /* choose a bunch of continous threads */ + if (boot_cpuid > nr_cpu_ids - 1) { + head_thread = boot_cpuid - nr_cpu_ids + 1; + /* keep the mapping of logical and thread */ + cpu = head_thread; + } } if (boot_dn == NULL) continue; } else if (dn == boot_dn) continue; - for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) { + for (j = head_thread; j < nthreads && online_cnt < nr_cpu_ids; j++) { bool avail; DBG(" thread %d -> cpu %d (hard id %d)\n",
@@ -520,13 +528,15 @@ void __init smp_setup_cpu_maps(void) set_hard_smp_processor_id(cpu, be32_to_cpu(intserv[j])); set_cpu_possible(cpu, true); cpu++; + online_cnt++; } - if (cpu >= nr_cpu_ids) { + if (online_cnt >= nr_cpu_ids) { of_node_put(dn); break; } if (handling_bootdn) { + head_thread = 0; handling_bootdn = false; goto again; }
--
2.7.4