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Subject[RFC PATCH v3 03/11] RISC-V: Allow marking IPIs as suitable for remote FENCEs
Date
To do remote FENCEs (i.e. remote TLB flushes) using IPI calls on
the RISC-V kernel, we need hardware mechanism to directly inject
IPI from the RISC-V kernel instead of using SBI calls.

The upcoming ACLINT [M|S]SWI devices and AIA IMSIC devices allow
direct IPI injection from the RISC-V kernel. To support this, we
extend the riscv_ipi_set_virq_range() function so that irqchip
drivers can mark IPIs as suitable for remote FENCEs.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
arch/riscv/include/asm/smp.h | 18 ++++++++++++++++--
arch/riscv/kernel/sbi-ipi.c | 2 +-
arch/riscv/kernel/smp.c | 9 ++++++++-
3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 6bdaab122ffa..f4856c911335 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -16,6 +16,9 @@ struct seq_file;
extern unsigned long boot_cpu_hartid;

#ifdef CONFIG_SMP
+
+#include <linux/jump_label.h>
+
/*
* Mapping between linux logical cpu index and hartid.
*/
@@ -47,7 +50,12 @@ void riscv_ipi_disable(void);
void riscv_ipi_setup(void);

/* Set the IPI interrupt numbers for arch (called by irqchip drivers) */
-void riscv_ipi_set_virq_range(int virq, int nr_irqs);
+void riscv_ipi_set_virq_range(int virq, int nr_irqs, bool use_for_rfence);
+
+/* Check if we can use IPIs for remote FENCEs */
+DECLARE_STATIC_KEY_FALSE(riscv_ipi_for_rfence);
+#define riscv_use_ipi_for_rfence() \
+ static_branch_unlikely(&riscv_ipi_for_rfence)

/* Secondary hart entry */
asmlinkage void smp_callin(void);
@@ -102,10 +110,16 @@ static inline void riscv_ipi_setup(void)
{
}

-static inline void riscv_ipi_set_virq_range(int virq, int nr)
+static inline void riscv_ipi_set_virq_range(int virq, int nr,
+ bool use_for_rfence)
{
}

+static inline bool riscv_use_ipi_for_rfence(void)
+{
+ return false;
+}
+
#endif /* CONFIG_SMP */

#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)
diff --git a/arch/riscv/kernel/sbi-ipi.c b/arch/riscv/kernel/sbi-ipi.c
index dc284ad3551c..c65daf50ff1f 100644
--- a/arch/riscv/kernel/sbi-ipi.c
+++ b/arch/riscv/kernel/sbi-ipi.c
@@ -149,7 +149,7 @@ static int __init sbi_ipi_set_virq(void)
return -ENOMEM;
}

- riscv_ipi_set_virq_range(virq, BITS_PER_LONG);
+ riscv_ipi_set_virq_range(virq, BITS_PER_LONG, false);

return 0;
}
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 6c9873b7d60e..a8ce7a0556ab 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -183,7 +183,10 @@ void riscv_ipi_setup(void)
riscv_ipi_enable();
}

-void riscv_ipi_set_virq_range(int virq, int nr)
+DEFINE_STATIC_KEY_FALSE(riscv_ipi_for_rfence);
+EXPORT_SYMBOL_GPL(riscv_ipi_for_rfence);
+
+void riscv_ipi_set_virq_range(int virq, int nr, bool use_for_rfence)
{
if (WARN_ON(ipi_virq_base))
return;
@@ -191,6 +194,10 @@ void riscv_ipi_set_virq_range(int virq, int nr)
WARN_ON(nr < IPI_MAX);
nr_ipi = min(nr, IPI_MAX);
ipi_virq_base = virq;
+ if (use_for_rfence)
+ static_branch_enable(&riscv_ipi_for_rfence);
+ else
+ static_branch_disable(&riscv_ipi_for_rfence);
}
EXPORT_SYMBOL_GPL(riscv_ipi_set_virq_range);

--
2.25.1
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