[PATCH RFC] ARM64: Add cpu hotplug for device tree parking method
From: Pratyush Anand
Date: Thu Dec 17 2015 - 08:41:00 EST
This patch has been implemented for CPU hotplug support for device tree
spin-table based parking method.
While cpu is offlined, cpu_die is called and when it is brought online
cpu_boot is called. So, cpu_boot must wake secondary and release pen,
otherwise dynamic cpu offline/online will not work.
Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
---
Hi,
Actually this patch is using some infrastructure from Geoff's kexec-v12.3.
But I am sending this patch for your review and feedback in advance. This
patch is needed for kexec and cpu hotplug to work on a system with device
tree spin-table method.
Have tested this patch with kexec and also with cpu offline from sys
interface.
# lscpu
Architecture: aarch64
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 4
# echo 0 > /sys/bus/cpu/devices/cpu3/online
# lscpu
Architecture: aarch64
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-2,4-7
Off-line CPU(s) list: 3
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 4
# echo 1 > /sys/bus/cpu/devices/cpu3/online
# lscpu
Architecture: aarch64
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 4
cpu-park infrastructure of this patch can further be shared by ACPI parking
protocol support for providing CPU hotplug support.
~Pratyush
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/cpu-park.S | 54 ++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/cpu-park.h | 25 ++++++++++++++++++
arch/arm64/kernel/smp_spin_table.c | 40 +++++++++++++++++++++++-----
4 files changed, 113 insertions(+), 8 deletions(-)
create mode 100644 arch/arm64/kernel/cpu-park.S
create mode 100644 arch/arm64/kernel/cpu-park.h
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index a08b0545bffa..f229f3d4b455 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -17,7 +17,7 @@ arm64-obj-y := debug-monitors.o entry.o irq.o fpsimd.o \
hyp-stub.o psci.o psci-call.o cpu_ops.o insn.o \
return_address.o cpuinfo.o cpu_errata.o \
cpufeature.o alternative.o cacheinfo.o \
- smp.o smp_spin_table.o topology.o
+ smp.o smp_spin_table.o cpu-park.o topology.o
extra-$(CONFIG_EFI) := efi-entry.o
diff --git a/arch/arm64/kernel/cpu-park.S b/arch/arm64/kernel/cpu-park.S
new file mode 100644
index 000000000000..7e80ecf24f28
--- /dev/null
+++ b/arch/arm64/kernel/cpu-park.S
@@ -0,0 +1,54 @@
+/*
+ * cpu park routines
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/sysreg.h>
+#include <asm/virt.h>
+
+.text
+.pushsection .idmap.text, "ax"
+
+/*
+ * __cpu_park(el2_switch, park_address) - Helper for cpu_park
+ *
+ * @el2_switch: Flag to indicate a swich to EL2 is needed, passed to cpu_park.
+ * @park_address - where cpu will keep on looking for address to jump
+ *
+ * Put the CPU into the wfe and check for valid none zero secondary address
+ * at parked address when a event is received. If secondary address is
+ * valid then jump to it.
+ */
+
+ENTRY(__cpu_park)
+ /* Clear sctlr_el1 flags. */
+ mrs x12, sctlr_el1
+ ldr x13, =SCTLR_ELx_FLAGS
+ bic x12, x12, x13
+ msr sctlr_el1, x12
+ isb
+1:
+ wfe
+ ldr x3, [x1] // get entry address
+ cmp x3, #0
+ b.eq 1b
+
+ mov x2, 0
+ str x2, [x1]
+
+ cbz x0, 2f // el2_switch?
+
+ mov x0, x3 // entry
+ hvc #HVC_CALL_FUNC // no return
+
+2:
+ ret x3
+
+ENDPROC(__cpu_park)
+
+.popsection
diff --git a/arch/arm64/kernel/cpu-park.h b/arch/arm64/kernel/cpu-park.h
new file mode 100644
index 000000000000..356438d21360
--- /dev/null
+++ b/arch/arm64/kernel/cpu-park.h
@@ -0,0 +1,25 @@
+/*
+ * cpu park routines
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _ARM64_CPU_PARK_H
+#define _ARM64_CPU_PARK_H
+
+#include <asm/virt.h>
+
+void __cpu_park(unsigned long el2_switch, unsigned long park_address);
+
+static inline void __noreturn cpu_park(unsigned long el2_switch,
+ unsigned long park_address)
+{
+ typeof(__cpu_park) *park_fn;
+ park_fn = (void *)virt_to_phys(__cpu_park);
+ park_fn(el2_switch, park_address);
+ unreachable();
+}
+
+#endif
diff --git a/arch/arm64/kernel/smp_spin_table.c b/arch/arm64/kernel/smp_spin_table.c
index aef3605a8c47..9411b9f59f9e 100644
--- a/arch/arm64/kernel/smp_spin_table.c
+++ b/arch/arm64/kernel/smp_spin_table.c
@@ -26,8 +26,11 @@
#include <asm/cpu_ops.h>
#include <asm/cputype.h>
#include <asm/io.h>
+#include <asm/kexec.h>
#include <asm/smp_plat.h>
+#include "cpu-park.h"
+
extern void secondary_holding_pen(void);
volatile unsigned long secondary_holding_pen_release = INVALID_HWID;
@@ -73,11 +76,16 @@ static int smp_spin_table_cpu_init(unsigned int cpu)
static int smp_spin_table_cpu_prepare(unsigned int cpu)
{
- __le64 __iomem *release_addr;
-
if (!cpu_release_addr[cpu])
return -ENODEV;
+ return 0;
+}
+
+static int smp_spin_table_cpu_boot(unsigned int cpu)
+{
+ __le64 __iomem *release_addr;
+
/*
* The cpu-release-addr may or may not be inside the linear mapping.
* As ioremap_cache will either give us a new mapping or reuse the
@@ -107,11 +115,6 @@ static int smp_spin_table_cpu_prepare(unsigned int cpu)
iounmap(release_addr);
- return 0;
-}
-
-static int smp_spin_table_cpu_boot(unsigned int cpu)
-{
/*
* Update the pen release flag.
*/
@@ -125,9 +128,32 @@ static int smp_spin_table_cpu_boot(unsigned int cpu)
return 0;
}
+#ifdef CONFIG_HOTPLUG_CPU
+static int smp_spin_table_cpu_disable(unsigned int cpu)
+{
+ if (!cpu_release_addr[cpu])
+ return -EOPNOTSUPP;
+
+ return 0;
+}
+
+static void smp_spin_table_cpu_die(unsigned int cpu)
+{
+ setup_mm_for_reboot();
+ cpu_park(in_crash_kexec ? 0 : is_hyp_mode_available(),
+ cpu_release_addr[cpu]);
+
+ pr_crit("unable to power off CPU%u\n", cpu);
+}
+#endif
+
const struct cpu_operations smp_spin_table_ops = {
.name = "spin-table",
.cpu_init = smp_spin_table_cpu_init,
.cpu_prepare = smp_spin_table_cpu_prepare,
.cpu_boot = smp_spin_table_cpu_boot,
+#ifdef CONFIG_HOTPLUG_CPU
+ .cpu_disable = smp_spin_table_cpu_disable,
+ .cpu_die = smp_spin_table_cpu_die,
+#endif
};
--
2.5.0
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