linux-dev/arch/riscv/include/asm/cpu_ops.h, branch linus/master

RISC-V: Use __cpu_up_stack/task_pointer only for spinwait method

2022-01-20T17:27:08Z

The __cpu_up_stack/task_pointer array is only used for spinwait method now. The per cpu array based lookup is also fragile for platforms with discontiguous/sparse hartids. The spinwait method is only used for M-mode Linux or older firmwares without SBI HSM extension. For general Linux systems, ordered booting method is preferred anyways to support cpu hotplug and kexec. Make sure that __cpu_up_stack/task_pointer is only used for spinwait method. Take this opportunity to rename it to __cpu_spinwait_stack/task_pointer to emphasize the purpose as well. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Signed-off-by: Palmer Dabbelt

RISC-V: Support cpu hotplug

2020-03-31T18:28:30Z

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 Reviewed-by: Anup Patel

RISC-V: Add cpu_ops and modify default booting method

2020-03-31T18:25:56Z

Currently, all non-booting harts start booting after the booting hart updates the per-hart stack pointer. This is done in a way that, it's difficult to implement any other booting method without breaking the backward compatibility. Define a cpu_ops method that allows to introduce other booting methods in future. Modify the current booting method to be compatible with cpu_ops. Signed-off-by: Atish Patra Reviewed-by: Anup Patel Signed-off-by: Palmer Dabbelt