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Date: Thu, 20 Jan 2022 01:09:15 -0800
From: Atish Patra <atishp@...osinc.com>
To: linux-kernel@...r.kernel.org
Cc: Atish Patra <atishp@...osinc.com>,
Anup Patel <anup@...infault.org>,
Albert Ou <aou@...s.berkeley.edu>,
Atish Patra <atishp@...shpatra.org>,
Damien Le Moal <damien.lemoal@....com>,
devicetree@...r.kernel.org, Jisheng Zhang <jszhang@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
linux-riscv@...ts.infradead.org,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Rob Herring <robh+dt@...nel.org>
Subject: [PATCH v3 3/6] RISC-V: Use __cpu_up_stack/task_pointer only for spinwait method
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 <anup@...infault.org>
Signed-off-by: Atish Patra <atishp@...osinc.com>
---
arch/riscv/include/asm/cpu_ops.h | 2 --
arch/riscv/kernel/cpu_ops.c | 16 ----------------
arch/riscv/kernel/cpu_ops_spinwait.c | 27 ++++++++++++++++++++++++++-
arch/riscv/kernel/head.S | 4 ++--
arch/riscv/kernel/head.h | 4 ++--
5 files changed, 30 insertions(+), 23 deletions(-)
diff --git a/arch/riscv/include/asm/cpu_ops.h b/arch/riscv/include/asm/cpu_ops.h
index a8ec3c5c1bd2..134590f1b843 100644
--- a/arch/riscv/include/asm/cpu_ops.h
+++ b/arch/riscv/include/asm/cpu_ops.h
@@ -40,7 +40,5 @@ struct cpu_operations {
extern const struct cpu_operations *cpu_ops[NR_CPUS];
void __init cpu_set_ops(int cpu);
-void cpu_update_secondary_bootdata(unsigned int cpuid,
- struct task_struct *tidle);
#endif /* ifndef __ASM_CPU_OPS_H */
diff --git a/arch/riscv/kernel/cpu_ops.c b/arch/riscv/kernel/cpu_ops.c
index 3f5a38b03044..c1e30f403c3b 100644
--- a/arch/riscv/kernel/cpu_ops.c
+++ b/arch/riscv/kernel/cpu_ops.c
@@ -8,31 +8,15 @@
#include <linux/of.h>
#include <linux/string.h>
#include <linux/sched.h>
-#include <linux/sched/task_stack.h>
#include <asm/cpu_ops.h>
#include <asm/sbi.h>
#include <asm/smp.h>
const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
-void *__cpu_up_stack_pointer[NR_CPUS] __section(".data");
-void *__cpu_up_task_pointer[NR_CPUS] __section(".data");
-
extern const struct cpu_operations cpu_ops_sbi;
extern const struct cpu_operations cpu_ops_spinwait;
-void cpu_update_secondary_bootdata(unsigned int cpuid,
- struct task_struct *tidle)
-{
- int hartid = cpuid_to_hartid_map(cpuid);
-
- /* 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);
-}
-
void __init cpu_set_ops(int cpuid)
{
#if IS_ENABLED(CONFIG_RISCV_SBI)
diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c
index b2c957bb68c1..346847f6c41c 100644
--- a/arch/riscv/kernel/cpu_ops_spinwait.c
+++ b/arch/riscv/kernel/cpu_ops_spinwait.c
@@ -6,11 +6,36 @@
#include <linux/errno.h>
#include <linux/of.h>
#include <linux/string.h>
+#include <linux/sched/task_stack.h>
#include <asm/cpu_ops.h>
#include <asm/sbi.h>
#include <asm/smp.h>
const struct cpu_operations cpu_ops_spinwait;
+void *__cpu_spinwait_stack_pointer[NR_CPUS] __section(".data");
+void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data");
+
+static void cpu_update_secondary_bootdata(unsigned int cpuid,
+ struct task_struct *tidle)
+{
+ int hartid = cpuid_to_hartid_map(cpuid);
+
+ /*
+ * The hartid must be less than NR_CPUS to avoid out-of-bound access
+ * errors for __cpu_spinwait_stack/task_pointer. That is not always possible
+ * for platforms with discontiguous hartid numbering scheme. That's why
+ * spinwait booting is not the recommended approach for any platforms
+ * booting Linux in S-mode and can be disabled in the future.
+ */
+ if (hartid == INVALID_HARTID || hartid >= NR_CPUS)
+ return;
+
+ /* Make sure tidle is updated */
+ smp_mb();
+ WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid],
+ task_stack_page(tidle) + THREAD_SIZE);
+ WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
+}
static int spinwait_cpu_prepare(unsigned int cpuid)
{
@@ -28,7 +53,7 @@ static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
* selects the first cpu to boot the kernel and causes the remainder
* of the cpus to spin in a loop waiting for their stack pointer to be
* setup by that main cpu. Writing to bootdata
- * (i.e __cpu_up_stack_pointer) signals to the spinning cpus that they
+ * (i.e __cpu_spinwait_stack_pointer) signals to the spinning cpus that they
* can continue the boot process.
*/
cpu_update_secondary_bootdata(cpuid, tidle);
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index bc24a90ede1c..1f11de45df9c 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -346,9 +346,9 @@ clear_bss_done:
csrw CSR_TVEC, a3
slli a3, a0, LGREG
- la a1, __cpu_up_stack_pointer
+ la a1, __cpu_spinwait_stack_pointer
XIP_FIXUP_OFFSET a1
- la a2, __cpu_up_task_pointer
+ la a2, __cpu_spinwait_task_pointer
XIP_FIXUP_OFFSET a2
add a1, a3, a1
add a2, a3, a2
diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
index aabbc3ac3e48..5393cca77790 100644
--- a/arch/riscv/kernel/head.h
+++ b/arch/riscv/kernel/head.h
@@ -16,7 +16,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa);
asmlinkage void __init __copy_data(void);
#endif
-extern void *__cpu_up_stack_pointer[];
-extern void *__cpu_up_task_pointer[];
+extern void *__cpu_spinwait_stack_pointer[];
+extern void *__cpu_spinwait_task_pointer[];
#endif /* __ASM_HEAD_H */
--
2.30.2
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