Unverified Commit 2ffc48fc authored by Atish Patra's avatar Atish Patra Committed by Palmer Dabbelt
Browse files

RISC-V: Move spinwait booting method to its own config 



The spinwait booting method should only be used for platforms with older
firmware without SBI HSM extension or M-mode firmware because spinwait
method can't support cpu hotplug, kexec or sparse hartid. It is better
to move the entire spinwait implementation to its own config which can
be disabled if required. It is enabled by default to maintain backward
compatibility and M-mode Linux.

Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Signed-off-by: default avatarAtish Patra <atishp@rivosinc.com>
Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 0b39eb38

arch/riscv/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -374,6 +374,20 @@ config RISCV_SBI_V01 
	  This config allows kernel to use SBI v0.1 APIs. This will be

	  deprecated in future once legacy M-mode software are no longer in use.



config RISCV_BOOT_SPINWAIT

	bool "Spinwait booting method"

	depends on SMP

	default y

	help

	  This enables support for booting Linux via spinwait method. In the

	  spinwait method, all cores randomly jump to Linux. One of the cores

	  gets chosen via lottery and all other keep spinning on a percpu

	  variable. This method cannot support CPU hotplug and sparse hartid

	  scheme. It should be only enabled for M-mode Linux or platforms relying

	  on older firmware without SBI HSM extension. All other platforms should

	  rely on ordered booting via SBI HSM extension which gets chosen

	  dynamically at runtime if the firmware supports it.



config KEXEC

	bool "Kexec system call"

	select KEXEC_CORE

arch/riscv/kernel/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -43,7 +43,8 @@ obj-$(CONFIG_FPU) += fpu.o 
obj-$(CONFIG_SMP)		+= smpboot.o

obj-$(CONFIG_SMP)		+= smp.o

obj-$(CONFIG_SMP)		+= cpu_ops.o

obj-$(CONFIG_SMP)		+= cpu_ops_spinwait.o



obj-$(CONFIG_RISCV_BOOT_SPINWAIT) += cpu_ops_spinwait.o

obj-$(CONFIG_MODULES)		+= module.o

obj-$(CONFIG_MODULE_SECTIONS)	+= module-sections.o

arch/riscv/kernel/cpu_ops.c

+8 −0
Original line number Diff line number Diff line
@@ -15,7 +15,15 @@ 
const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;



extern const struct cpu_operations cpu_ops_sbi;

#ifdef CONFIG_RISCV_BOOT_SPINWAIT

extern const struct cpu_operations cpu_ops_spinwait;

#else

const struct cpu_operations cpu_ops_spinwait = {

	.name		= "",

	.cpu_prepare	= NULL,

	.cpu_start	= NULL,

};

#endif



void __init cpu_set_ops(int cpuid)

{

arch/riscv/kernel/head.S

+4 −4
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ pmp_done: 
	li t0, SR_FS

	csrc CSR_STATUS, t0



#ifdef CONFIG_SMP

#ifdef CONFIG_RISCV_BOOT_SPINWAIT

	li t0, CONFIG_NR_CPUS

	blt a0, t0, .Lgood_cores

	tail .Lsecondary_park
@@ -285,7 +285,7 @@ pmp_done: 
	beq t0, t1, .Lsecondary_start



#endif /* CONFIG_XIP */

#endif /* CONFIG_SMP */

#endif /* CONFIG_RISCV_BOOT_SPINWAIT */



#ifdef CONFIG_XIP_KERNEL

	la sp, _end + THREAD_SIZE
@@ -344,7 +344,7 @@ clear_bss_done: 
	call soc_early_init

	tail start_kernel



#ifdef CONFIG_SMP

#if CONFIG_RISCV_BOOT_SPINWAIT

.Lsecondary_start:

	/* Set trap vector to spin forever to help debug */

	la a3, .Lsecondary_park
@@ -371,7 +371,7 @@ clear_bss_done: 
	fence



	tail .Lsecondary_start_common

#endif

#endif /* CONFIG_RISCV_BOOT_SPINWAIT */



END(_start_kernel)

arch/riscv/kernel/head.h

+2 −0
Original line number Diff line number Diff line
@@ -16,7 +16,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa); 
asmlinkage void __init __copy_data(void);

#endif



#ifdef CONFIG_RISCV_BOOT_SPINWAIT

extern void *__cpu_spinwait_stack_pointer[];

extern void *__cpu_spinwait_task_pointer[];

#endif



#endif /* __ASM_HEAD_H */