linux-kernel - [RFC 07/12] riscv: Handle pseudo NMI in arch irq handler

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Date:   Mon, 23 Oct 2023 16:29:06 +0800
From:   Xu Lu <luxu.kernel@...edance.com>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, tglx@...utronix.de, maz@...nel.org,
        anup@...infault.org, atishp@...shpatra.org
Cc:     dengliang.1214@...edance.com, liyu.yukiteru@...edance.com,
        sunjiadong.lff@...edance.com, xieyongji@...edance.com,
        lihangjing@...edance.com, chaiwen.cc@...edance.com,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Xu Lu <luxu.kernel@...edance.com>
Subject: [RFC 07/12] riscv: Handle pseudo NMI in arch irq handler

This commit handles pseudo NMI in arch irq handler. We enter NMI context
before handling NMI and keeps all interrupts disabled during NMI handling
to avoid interrupt nesting.

Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
Signed-off-by: Hangjing Li <lihangjing@...edance.com>
---
 drivers/irqchip/irq-riscv-intc.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
index 83a0a744fce6..c672c0c64d5d 100644
--- a/drivers/irqchip/irq-riscv-intc.c
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -20,6 +20,26 @@
 
 static struct irq_domain *intc_domain;
 
+#ifdef CONFIG_RISCV_PSEUDO_NMI
+
+static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
+{
+	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
+
+	if (unlikely(cause >= BITS_PER_LONG))
+		panic("unexpected interrupt cause");
+
+	if (is_nmi(cause)) {
+		nmi_enter();
+		generic_handle_domain_nmi(intc_domain, cause);
+		nmi_exit();
+	} else {
+		generic_handle_domain_irq(intc_domain, cause);
+	}
+}
+
+#else /* CONFIG_RISCV_PSEUDO_NMI */
+
 static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
 {
 	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
@@ -30,6 +50,8 @@ static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
 	generic_handle_domain_irq(intc_domain, cause);
 }
 
+#endif /* CONFIG_RISCV_PSEUDO_NMI */
+
 /*
  * On RISC-V systems local interrupts are masked or unmasked by writing
  * the SIE (Supervisor Interrupt Enable) CSR.  As CSRs can only be written
-- 
2.20.1