From 9a2451f1866344d38b4a1dc20396e3a03954fcd7 Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Thu, 20 Jan 2022 01:09:13 -0800 Subject: RISC-V: Avoid using per cpu array for ordered booting Currently both order booting and spinwait approach uses a per cpu array to update stack & task pointer. This approach will not work for the following cases. 1. If NR_CPUs are configured to be less than highest hart id. 2. A platform has sparse hartid. This issue can be fixed for ordered booting as the booting cpu brings up one cpu at a time using SBI HSM extension which has opaque parameter that is unused until now. Introduce a common secondary boot data structure that can store the stack and task pointer. Secondary harts will use this data while booting up to setup the sp & tp. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/cpu_ops_sbi.h | 25 +++++++++++++++++++++++++ arch/riscv/kernel/asm-offsets.c | 3 +++ arch/riscv/kernel/cpu_ops_sbi.c | 26 ++++++++++++++++++++------ arch/riscv/kernel/head.S | 19 ++++++++++--------- 4 files changed, 58 insertions(+), 15 deletions(-) create mode 100644 arch/riscv/include/asm/cpu_ops_sbi.h (limited to 'arch') diff --git a/arch/riscv/include/asm/cpu_ops_sbi.h b/arch/riscv/include/asm/cpu_ops_sbi.h new file mode 100644 index 000000000000..56e4b76d09ff --- /dev/null +++ b/arch/riscv/include/asm/cpu_ops_sbi.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2021 by Rivos Inc. + */ +#ifndef __ASM_CPU_OPS_SBI_H +#define __ASM_CPU_OPS_SBI_H + +#ifndef __ASSEMBLY__ +#include +#include +#include + +/** + * struct sbi_hart_boot_data - Hart specific boot used during booting and + * cpu hotplug. + * @task_ptr: A pointer to the hart specific tp + * @stack_ptr: A pointer to the hart specific sp + */ +struct sbi_hart_boot_data { + void *task_ptr; + void *stack_ptr; +}; +#endif + +#endif /* ifndef __ASM_CPU_OPS_SBI_H */ diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index 253126e4beef..df0519a64eaf 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -12,6 +12,7 @@ #include #include #include +#include void asm_offsets(void); @@ -468,4 +469,6 @@ void asm_offsets(void) DEFINE(PT_SIZE_ON_STACK, ALIGN(sizeof(struct pt_regs), STACK_ALIGN)); OFFSET(KERNEL_MAP_VIRT_ADDR, kernel_mapping, virt_addr); + OFFSET(SBI_HART_BOOT_TASK_PTR_OFFSET, sbi_hart_boot_data, task_ptr); + OFFSET(SBI_HART_BOOT_STACK_PTR_OFFSET, sbi_hart_boot_data, stack_ptr); } diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c index 685fae72b7f5..dae29cbfe550 100644 --- a/arch/riscv/kernel/cpu_ops_sbi.c +++ b/arch/riscv/kernel/cpu_ops_sbi.c @@ -7,13 +7,22 @@ #include #include +#include #include +#include #include #include extern char secondary_start_sbi[]; const struct cpu_operations cpu_ops_sbi; +/* + * Ordered booting via HSM brings one cpu at a time. However, cpu hotplug can + * be invoked from multiple threads in parallel. Define a per cpu data + * to handle that. + */ +DEFINE_PER_CPU(struct sbi_hart_boot_data, boot_data); + static int sbi_hsm_hart_start(unsigned long hartid, unsigned long saddr, unsigned long priv) { @@ -55,14 +64,19 @@ static int sbi_hsm_hart_get_status(unsigned long hartid) static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle) { - int rc; unsigned long boot_addr = __pa_symbol(secondary_start_sbi); int hartid = cpuid_to_hartid_map(cpuid); - - cpu_update_secondary_bootdata(cpuid, tidle); - rc = sbi_hsm_hart_start(hartid, boot_addr, 0); - - return rc; + unsigned long hsm_data; + struct sbi_hart_boot_data *bdata = &per_cpu(boot_data, cpuid); + + /* Make sure tidle is updated */ + smp_mb(); + bdata->task_ptr = tidle; + bdata->stack_ptr = task_stack_page(tidle) + THREAD_SIZE; + /* Make sure boot data is updated */ + smp_mb(); + hsm_data = __pa(bdata); + return sbi_hsm_hart_start(hartid, boot_addr, hsm_data); } static int sbi_cpu_prepare(unsigned int cpuid) diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index db4be6a7e392..05ea372e1909 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include "efi-header.S" @@ -168,15 +169,15 @@ secondary_start_sbi: la a3, .Lsecondary_park csrw CSR_TVEC, a3 - slli a3, a0, LGREG - la a4, __cpu_up_stack_pointer - XIP_FIXUP_OFFSET a4 - la a5, __cpu_up_task_pointer - XIP_FIXUP_OFFSET a5 - add a4, a3, a4 - add a5, a3, a5 - REG_L sp, (a4) - REG_L tp, (a5) + /* a0 contains the hartid & a1 contains boot data */ + li a2, SBI_HART_BOOT_TASK_PTR_OFFSET + XIP_FIXUP_OFFSET a2 + add a2, a2, a1 + REG_L tp, (a2) + li a3, SBI_HART_BOOT_STACK_PTR_OFFSET + XIP_FIXUP_OFFSET a3 + add a3, a3, a1 + REG_L sp, (a3) .Lsecondary_start_common: -- cgit v1.2.3