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[99.13.229.45]) by smtp.gmail.com with ESMTPSA id r6sm3272402pjg.21.2021.12.03.16.20.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Dec 2021 16:20:52 -0800 (PST) From: Atish Patra To: linux-kernel@vger.kernel.org Cc: Atish Patra , Alexandre Ghiti , Anup Patel , Greentime Hu , Guo Ren , Heinrich Schuchardt , Ingo Molnar , Jisheng Zhang , kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, linux-riscv@lists.infradead.org, Marc Zyngier , Nanyong Sun , Nick Kossifidis , Palmer Dabbelt , Paul Walmsley , Pekka Enberg , Vincent Chen , Vitaly Wool Subject: [RFC 1/6] RISC-V: Avoid using per cpu array for ordered booting Date: Fri, 3 Dec 2021 16:20:33 -0800 Message-Id: <20211204002038.113653-2-atishp@atishpatra.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211204002038.113653-1-atishp@atishpatra.org> References: <20211204002038.113653-1-atishp@atishpatra.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Atish Patra 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. Signed-off-by: Atish Patra --- arch/riscv/include/asm/cpu_ops_sbi.h | 28 ++++++++++++++++++++++++++++ arch/riscv/kernel/cpu_ops_sbi.c | 23 ++++++++++++++++++++--- arch/riscv/kernel/head.S | 19 ++++++++++--------- 3 files changed, 58 insertions(+), 12 deletions(-) create mode 100644 arch/riscv/include/asm/cpu_ops_sbi.h 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..ccb9a6d30486 --- /dev/null +++ b/arch/riscv/include/asm/cpu_ops_sbi.h @@ -0,0 +1,28 @@ +/* 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 + +#define SBI_HART_BOOT_TASK_PTR_OFFSET (0x00) +#define SBI_HART_BOOT_STACK_PTR_OFFSET RISCV_SZPTR + +#endif /* ifndef __ASM_CPU_OPS_H */ diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c index 685fae72b7f5..2e7a9dd9c2a7 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 paralle. 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) { @@ -58,9 +67,17 @@ 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); + 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); + rc = sbi_hsm_hart_start(hartid, boot_addr, hsm_data); return rc; } diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index f52f01ecbeea..40d4c625513c 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" @@ -167,15 +168,15 @@ 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) .global secondary_start_common secondary_start_common: