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RISC-V: Support cpu hotplug

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This patch enable support for cpu hotplug in RISC-V. It uses SBI HSM
extension to online/offline any hart. As a result, the harts are
returned to firmware once they are offline. If the harts are brought
online afterwards, they re-enter Linux kernel as if a secondary hart
booted for the first time. All booting requirements are honored during
this process.

Tested both on QEMU and HighFive Unleashed board with. Test result follows.

---------------------------------------------------
Offline cpu 2
---------------------------------------------------
$ echo 0 > /sys/devices/system/cpu/cpu2/online
[   32.828684] CPU2: off
$ cat /proc/cpuinfo
processor       : 0
hart            : 0
isa             : rv64imafdcsu
mmu             : sv48

processor       : 1
hart            : 1
isa             : rv64imafdcsu
mmu             : sv48

processor       : 3
hart            : 3
isa             : rv64imafdcsu
mmu             : sv48

processor       : 4
hart            : 4
isa             : rv64imafdcsu
mmu             : sv48

processor       : 5
hart            : 5
isa             : rv64imafdcsu
mmu             : sv48

processor       : 6
hart            : 6
isa             : rv64imafdcsu
mmu             : sv48

processor       : 7
hart            : 7
isa             : rv64imafdcsu
mmu             : sv48

---------------------------------------------------
online cpu 2
---------------------------------------------------
$ echo 1 > /sys/devices/system/cpu/cpu2/online
$ cat /proc/cpuinfo
processor       : 0
hart            : 0
isa             : rv64imafdcsu
mmu             : sv48

processor       : 1
hart            : 1
isa             : rv64imafdcsu
mmu             : sv48

processor       : 2
hart            : 2
isa             : rv64imafdcsu
mmu             : sv48

processor       : 3
hart            : 3
isa             : rv64imafdcsu
mmu             : sv48

processor       : 4
hart            : 4
isa             : rv64imafdcsu
mmu             : sv48

processor       : 5
hart            : 5
isa             : rv64imafdcsu
mmu             : sv48

processor       : 6
hart            : 6
isa             : rv64imafdcsu
mmu             : sv48

processor       : 7
hart            : 7
isa             : rv64imafdcsu
mmu             : sv48

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Atish Patra
2020-03-17 18:11:44 -07:00
committed by Palmer Dabbelt
parent cfafe26013
commit f1e58583b9
7 changed files with 180 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
arch/riscv/include/asm/cpu_ops.h
View File

@@ -18,12 +18,24 @@
* is a mechanism for doing so, tests whether it is
* possible to boot the given HART.
* @cpu_start: Boots a cpu into the kernel.
* @cpu_disable: Prepares a cpu to die. May fail for some
* mechanism-specific reason, which will cause the hot
* unplug to be aborted. Called from the cpu to be killed.
* @cpu_stop: Makes a cpu leave the kernel. Must not fail. Called from
* the cpu being stopped.
* @cpu_is_stopped: Ensures a cpu has left the kernel. Called from another
* cpu.
*/
struct cpu_operations {
const char *name;
int (*cpu_prepare)(unsigned int cpu);
int (*cpu_start)(unsigned int cpu,
struct task_struct *tidle);
#ifdef CONFIG_HOTPLUG_CPU
int (*cpu_disable)(unsigned int cpu);
void (*cpu_stop)(void);
int (*cpu_is_stopped)(unsigned int cpu);
#endif
};
extern const struct cpu_operations *cpu_ops[NR_CPUS];