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Subject[PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent
Date
Previously, we build the apicid <--> cpuid mapping when the cpu is present, but
the relationship will be changed if the cpu/node hotplug happenned, because we
always choose the first free cpuid for the hot added cpu (whether it is new-add
or re-add), so this the cpuid <--> node mapping changed if node hot plug
occurred, and it causes the wq sub-system allocation failture:
==
SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
cache: kmalloc-192, object size: 192, buffer size: 192, default
order:
1, min order: 0
node 0: slabs: 6172, objs: 259224, free: 245741
node 1: slabs: 3261, objs: 136962, free: 127656
==
So here we build the persistent [lapic id] <--> cpuid mapping when the cpu first
present, and never change it.

Suggested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
---
arch/x86/kernel/apic/apic.c | 31 ++++++++++++++++++++++++++++++-
1 files changed, 30 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index ad3639a..d539ebc 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2038,6 +2038,30 @@ void disconnect_bsp_APIC(int virt_wire_setup)
apic_write(APIC_LVT1, value);
}

+/*
+ * Logic cpu number(cpuid) to local APIC id persistent mappings.
+ * Do not clear the mapping even if cpu hot removed.
+ * */
+static int apicid_to_x86_cpu[MAX_LOCAL_APIC] = {
+ [0 ... MAX_LOCAL_APIC - 1] = -1,
+};
+
+/*
+ * Internal cpu id bits, set the bit once cpu present, and never clear it.
+ * */
+static cpumask_t cpuid_mask = CPU_MASK_NONE;
+
+static int get_cpuid(int apicid)
+{
+ int cpuid;
+
+ cpuid = apicid_to_x86_cpu[apicid];
+ if (cpuid == -1)
+ cpuid = cpumask_next_zero(-1, &cpuid_mask);
+
+ return cpuid;
+}
+
int generic_processor_info(int apicid, int version)
{
int cpu, max = nr_cpu_ids;
@@ -2115,7 +2139,10 @@ int generic_processor_info(int apicid, int version)
*/
cpu = 0;
} else
- cpu = cpumask_next_zero(-1, cpu_present_mask);
+ cpu = get_cpuid(apicid);
+
+ /* Store the mapping */
+ apicid_to_x86_cpu[apicid] = cpu;

/*
* Validate version
@@ -2144,6 +2171,8 @@ int generic_processor_info(int apicid, int version)
early_per_cpu(x86_cpu_to_logical_apicid, cpu) =
apic->x86_32_early_logical_apicid(cpu);
#endif
+ /* Mark this cpu id as uesed (already mapping a local apic id) */
+ cpumask_set_cpu(cpu, &cpuid_mask);
set_cpu_possible(cpu, true);
set_cpu_present(cpu, true);

--
1.7.7


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