linux-kernel - [PATCH V5 09/11] riscv: Support HAVE_SOFTIRQ_ON_OWN

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Date:   Sun, 18 Sep 2022 11:52:44 -0400
From:   guoren@...nel.org
To:     arnd@...db.de, guoren@...nel.org, palmer@...osinc.com,
        tglx@...utronix.de, peterz@...radead.org, luto@...nel.org,
        conor.dooley@...rochip.com, heiko@...ech.de, jszhang@...nel.org,
        lazyparser@...il.com, falcon@...ylab.org, chenhuacai@...nel.org,
        apatel@...tanamicro.com, atishp@...shpatra.org, palmer@...belt.com,
        paul.walmsley@...ive.com, mark.rutland@....com,
        zouyipeng@...wei.com, bigeasy@...utronix.de,
        David.Laight@...lab.com
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: [PATCH V5 09/11] riscv: Support HAVE_SOFTIRQ_ON_OWN_STACK

From: Guo Ren <guoren@...ux.alibaba.com>

Add the HAVE_SOFTIRQ_ON_OWN_STACK feature for the IRQ_STACKS config. The
irq and softirq use the same independent irq_stack of percpu by time
division multiplexing.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 arch/riscv/Kconfig      |  7 ++++---
 arch/riscv/kernel/irq.c | 16 ++++++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 75db47a983f2..dfe600f3526c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -434,12 +434,13 @@ config FPU
 	  If you don't know what to do here, say Y.
 
 config IRQ_STACKS
-	bool "Independent irq stacks" if EXPERT
+	bool "Independent irq & softirq stacks" if EXPERT
 	default y
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
+	select HAVE_SOFTIRQ_ON_OWN_STACK
 	help
-	  Add independent irq stacks for percpu to prevent kernel stack overflows.
-	  We may save some memory footprint by disabling IRQ_STACKS.
+	  Add independent irq & softirq stacks for percpu to prevent kernel stack
+	  overflows. We may save some memory footprint by disabling IRQ_STACKS.
 
 endmenu # "Platform type"
 
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 5ad4952203c5..6dc9ccd01470 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -11,6 +11,7 @@
 #include <linux/seq_file.h>
 #include <asm/smp.h>
 #include <asm/vmap_stack.h>
+#include <asm/softirq_stack.h>
 
 #ifdef CONFIG_IRQ_STACKS
 static DEFINE_PER_CPU(ulong *, irq_stack_ptr);
@@ -38,6 +39,21 @@ static void init_irq_stacks(void)
 		per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack, cpu);
 }
 #endif /* CONFIG_VMAP_STACK */
+
+#ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
+static void do_riscv_softirq(struct pt_regs *regs)
+{
+	__do_softirq();
+}
+
+void do_softirq_own_stack(void)
+{
+	ulong *sp = per_cpu(irq_stack_ptr, smp_processor_id());
+
+	call_on_stack(NULL, sp, do_riscv_softirq, 0);
+}
+#endif /* CONFIG_SOFTIRQ_ON_OWN_STACK */
+
 #else
 static void init_irq_stacks(void) {}
 #endif /* CONFIG_IRQ_STACKS */
-- 
2.36.1