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Date: Mon, 27 Jan 2020 18:27:36 -0800
From: Atish Patra <atish.patra@....com>
To: linux-kernel@...r.kernel.org
Cc: Atish Patra <atish.patra@....com>,
Albert Ou <aou@...s.berkeley.edu>,
Anup Patel <anup@...infault.org>, Borislav Petkov <bp@...e.de>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Greentime Hu <greentime.hu@...ive.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Kees Cook <keescook@...omium.org>,
linux-riscv@...ts.infradead.org, Mao Han <han_mao@...ky.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Thomas Gleixner <tglx@...utronix.de>,
Vincent Chen <vincent.chen@...ive.com>, abner.chang@....com,
clin@...e.com, nickhu@...estech.com,
Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: [PATCH v7 09/10] RISC-V: Add supported for ordered booting method using HSM
Currently, all harts have to jump Linux in RISC-V. This complicates the
multi-stage boot process as every transient stage also has to ensure all
harts enter to that stage and jump to Linux afterwards. It also obstructs
a clean Kexec implementation.
SBI HSM extension provides alternate solutions where only a single hart
need to boot and enter Linux. The booting hart can bring up secondary
harts one by one afterwards.
Add SBI HSM based cpu_ops that implements an ordered booting method in
RISC-V. This change is also backward compatible with older firmware not
implementing HSM extension. If a latest kernel is used with older
firmware, it will continue to use the default spinning booting method.
Signed-off-by: Atish Patra <atish.patra@....com>
---
arch/riscv/kernel/cpu_ops.c | 41 ++++++++++++++++++++++++++++++++++++-
arch/riscv/kernel/head.S | 25 ++++++++++++++++++++++
arch/riscv/kernel/smpboot.c | 2 +-
arch/riscv/kernel/traps.c | 2 +-
4 files changed, 67 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/kernel/cpu_ops.c b/arch/riscv/kernel/cpu_ops.c
index 099dbb6ff9f0..454df032066f 100644
--- a/arch/riscv/kernel/cpu_ops.c
+++ b/arch/riscv/kernel/cpu_ops.c
@@ -17,9 +17,13 @@ const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
void *__cpu_up_stack_pointer[NR_CPUS];
void *__cpu_up_task_pointer[NR_CPUS];
+extern char secondary_start_sbi[];
+const struct cpu_operations cpu_sbi_ops;
const struct cpu_operations cpu_spinwait_ops;
+#define RISCV_HART_FIRMWARE_STOPPED 0
+
static int spinwait_cpu_prepare(unsigned int cpuid)
{
if (!cpu_spinwait_ops.cpu_start) {
@@ -29,6 +33,32 @@ static int spinwait_cpu_prepare(unsigned int cpuid)
return 0;
}
+static int sbi_cpu_prepare(unsigned int cpuid)
+{
+ if (!cpu_sbi_ops.cpu_start) {
+ pr_err("cpu start method not defined for CPU [%d]\n", cpuid);
+ return -ENODEV;
+ }
+ return 0;
+}
+
+static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
+{
+ int rc;
+ int hartid = cpuid_to_hartid_map(cpuid);
+ unsigned long boot_addr = __pa_symbol(secondary_start_sbi);
+
+ /* Make sure tidle is updated */
+ smp_mb();
+ WRITE_ONCE(__cpu_up_stack_pointer[hartid],
+ task_stack_page(tidle) + THREAD_SIZE);
+ WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
+
+ rc = sbi_hsm_hart_start(hartid, boot_addr, 0);
+
+ return rc;
+}
+
static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
{
int hartid = cpuid_to_hartid_map(cpuid);
@@ -48,6 +78,12 @@ static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
return 0;
}
+const struct cpu_operations cpu_sbi_ops = {
+ .name = "sbi",
+ .cpu_prepare = sbi_cpu_prepare,
+ .cpu_start = sbi_cpu_start,
+};
+
const struct cpu_operations cpu_spinwait_ops = {
.name = "spinwait",
.cpu_prepare = spinwait_cpu_prepare,
@@ -56,6 +92,9 @@ const struct cpu_operations cpu_spinwait_ops = {
int __init cpu_set_ops(int cpuid)
{
- cpu_ops[cpuid] = &cpu_spinwait_ops;
+ if (sbi_hsm_is_available())
+ cpu_ops[cpuid] = &cpu_sbi_ops;
+ else
+ cpu_ops[cpuid] = &cpu_spinwait_ops;
return 0;
}
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 9d7f084a50cc..3c93973667c8 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -210,11 +210,36 @@ relocate:
ret
#endif /* CONFIG_MMU */
#ifdef CONFIG_SMP
+ .global secondary_start_sbi
+secondary_start_sbi:
+ /* Mask all interrupts */
+ csrw CSR_IE, zero
+ csrw CSR_IP, zero
+
+ /* Load the global pointer */
+ .option push
+ .option norelax
+ la gp, __global_pointer$
+ .option pop
+
+ /*
+ * Disable FPU to detect illegal usage of
+ * floating point in kernel space
+ */
+ li t0, SR_FS
+ csrc CSR_STATUS, t0
+
/* Set trap vector to spin forever to help debug */
la a3, .Lsecondary_park
csrw CSR_TVEC, a3
slli a3, a0, LGREG
+ la a4, __cpu_up_stack_pointer
+ la a5, __cpu_up_task_pointer
+ add a4, a3, a4
+ add a5, a3, a5
+ REG_L sp, (a4)
+ REG_L tp, (a5)
.global secondary_start_common
secondary_start_common:
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index f2cf541bc895..8ac9115001b9 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -144,7 +144,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
/*
* C entry point for a secondary processor.
*/
-asmlinkage __visible void __init smp_callin(void)
+asmlinkage __visible void smp_callin(void)
{
struct mm_struct *mm = &init_mm;
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index f4cad5163bf2..0063dd7318d6 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -147,7 +147,7 @@ int is_valid_bugaddr(unsigned long pc)
}
#endif /* CONFIG_GENERIC_BUG */
-void __init trap_init(void)
+void trap_init(void)
{
/*
* Set sup0 scratch register to 0, indicating to exception vector
--
2.24.0
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