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    Subject[PATCH v9 5/7] 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 supervisor mode (i.e. RISC-V kernel) instead of using SBI calls.

    The upcoming AIA IMSIC devices allow direct IPI injection from the
    supervisor mode (i.e. RISC-V kernel). To support this, we extend the
    riscv_ipi_set_virq_range() function so that IPI provider (i.e. irqchip
    drivers can mark IPIs as suitable for remote FENCEs.

    Signed-off-by: Anup Patel <apatel@ventanamicro.com>
    ---
    arch/riscv/include/asm/smp.h | 18 ++++++++++++++++--
    arch/riscv/kernel/sbi-ipi.c | 2 +-
    arch/riscv/kernel/smp.c | 11 ++++++++++-
    drivers/clocksource/timer-clint.c | 2 +-
    4 files changed, 28 insertions(+), 5 deletions(-)

    diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
    index 79ed0b73cd4e..56976e41a21e 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.
    */
    @@ -46,7 +49,12 @@ void riscv_ipi_disable(void);
    bool riscv_ipi_have_virq_range(void);

    /* Set the IPI interrupt numbers for arch (called by irqchip drivers) */
    -void riscv_ipi_set_virq_range(int virq, int nr);
    +void riscv_ipi_set_virq_range(int virq, int nr, 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);
    @@ -93,10 +101,16 @@ static inline bool riscv_ipi_have_virq_range(void)
    return false;
    }

    -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 0bb070a5dcb4..27fdc394d2f0 100644
    --- a/arch/riscv/kernel/sbi-ipi.c
    +++ b/arch/riscv/kernel/sbi-ipi.c
    @@ -55,6 +55,6 @@ void __init sbi_ipi_init(void)
    return;
    }

    - riscv_ipi_set_virq_range(virq, BITS_PER_BYTE);
    + riscv_ipi_set_virq_range(virq, BITS_PER_BYTE, false);
    pr_info("providing IPIs using SBI IPI extension\n");
    }
    diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
    index e8a20454d65b..74b8cb1a89ab 100644
    --- a/arch/riscv/kernel/smp.c
    +++ b/arch/riscv/kernel/smp.c
    @@ -145,7 +145,10 @@ bool riscv_ipi_have_virq_range(void)
    return (ipi_virq_base) ? true : false;
    }

    -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)
    {
    int i, err;

    @@ -168,6 +171,12 @@ void riscv_ipi_set_virq_range(int virq, int nr)

    /* Enabled IPIs for boot CPU immediately */
    riscv_ipi_enable();
    +
    + /* Update RFENCE static key */
    + 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);

    diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
    index ac7c2caaa65a..f418816fd706 100644
    --- a/drivers/clocksource/timer-clint.c
    +++ b/drivers/clocksource/timer-clint.c
    @@ -246,7 +246,7 @@ static int __init clint_timer_init_dt(struct device_node *np)
    goto fail_remove_cpuhp;
    }

    - riscv_ipi_set_virq_range(virq, BITS_PER_BYTE);
    + riscv_ipi_set_virq_range(virq, BITS_PER_BYTE, true);
    clint_clear_ipi(clint_ipi_irq, NULL);

    return 0;
    --
    2.34.1
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