[PATCH] irqchip/mips: Fix RCU violation when using irqdomain lookup on interrupt entry

Marc Zyngier
2021-07-06T11:07:00Z

Since d4a45c68dc81 ("irqdomain: Protect the linear revmap with RCU"),
any irqdomain lookup requires the RCU read lock to be held.

This assumes that the architecture code will be structured such as
irq_enter() will be called *before* the interrupt is looked up
in the irq domain. However, this isn't the case for MIPS, and a number
of drivers are structured to do it the other way around when handling
an interrupt in their root irqchip (secondary irqchips are OK by
construction).

This results in a RCU splat on a lockdep-enabled kernel when the kernel
takes an interrupt from idle, as reported by Guenter Roeck.

Note that this could have fired previously if any driver had used
tree-based irqdomain, which always had the RCU requirement.

To solve this, provide a MIPS-specific helper (do_domain_IRQ())
as the pendent of do_IRQ() that will do thing in the right order
(and maybe save some cycles in the process).

Ideally, MIPS would be moved over to using handle_domain_irq(),
but that's much more ambitious.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20210705172352.GA56304@roeck-us.net
---
arch/mips/include/asm/irq.h | 3 +++
arch/mips/kernel/irq.c | 14 ++++++++++++++
drivers/irqchip/irq-mips-cpu.c | 10 ++++++----
drivers/irqchip/irq-mips-gic.c | 8 ++++----
drivers/irqchip/irq-pic32-evic.c | 5 ++---
5 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index d1477ecb1af9..57561e0e6e8d 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -57,6 +57,9 @@ asmlinkage void plat_irq_dispatch(void);

extern void do_IRQ(unsigned int irq);

+struct irq_domain;
+extern void do_domain_IRQ(struct irq_domain *domain, unsigned int irq);
+
extern void arch_init_irq(void);
extern void spurious_interrupt(void);

diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
index 85b6c60f285d..c76005cd3b79 100644
--- a/arch/mips/kernel/irq.c
+++ b/arch/mips/kernel/irq.c
@@ -21,6 +21,7 @@
#include <linux/kallsyms.h>
#include <linux/kgdb.h>
#include <linux/ftrace.h>
+#include <linux/irqdomain.h>

#include <linux/atomic.h>
#include <linux/uaccess.h>
@@ -107,3 +108,16 @@ void __irq_entry do_IRQ(unsigned int irq)
irq_exit();
}

+void __irq_entry do_domain_IRQ(struct irq_domain *domain, unsigned int hwirq)
+{
+ struct irq_desc *desc;
+
+ irq_enter();
+ check_stack_overflow();
+
+ desc = irq_resolve_mapping(domain, hwirq);
+ if (likely(desc))
+ handle_irq_desc(desc);
+
+ irq_exit();
+}
diff --git a/drivers/irqchip/irq-mips-cpu.c b/drivers/irqchip/irq-mips-cpu.c
index 0bbb0b2d0dd5..0c7ae71a0af0 100644
--- a/drivers/irqchip/irq-mips-cpu.c
+++ b/drivers/irqchip/irq-mips-cpu.c
@@ -127,7 +127,6 @@ static struct irq_chip mips_mt_cpu_irq_controller = {
asmlinkage void __weak plat_irq_dispatch(void)
{
unsigned long pending = read_c0_cause() & read_c0_status() & ST0_IM;
- unsigned int virq;
int irq;

if (!pending) {
@@ -137,12 +136,15 @@ asmlinkage void __weak plat_irq_dispatch(void)

pending >>= CAUSEB_IP;
while (pending) {
+ struct irq_domain *d;
+
irq = fls(pending) - 1;
if (IS_ENABLED(CONFIG_GENERIC_IRQ_IPI) && irq < 2)
- virq = irq_linear_revmap(ipi_domain, irq);
+ d = ipi_domain;
else
- virq = irq_linear_revmap(irq_domain, irq);
- do_IRQ(virq);
+ d = irq_domain;
+
+ do_domain_IRQ(d, irq);
pending &= ~BIT(irq);
}
}
diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index b146e069bf5b..54c7092cc61d 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -169,8 +169,8 @@ static void gic_handle_shared_int(bool chained)
generic_handle_domain_irq(gic_irq_domain,
GIC_SHARED_TO_HWIRQ(intr));
else
- do_IRQ(irq_find_mapping(gic_irq_domain,
- GIC_SHARED_TO_HWIRQ(intr)));
+ do_domain_IRQ(gic_irq_domain,
+ GIC_SHARED_TO_HWIRQ(intr));
}
}

@@ -320,8 +320,8 @@ static void gic_handle_local_int(bool chained)
generic_handle_domain_irq(gic_irq_domain,
GIC_LOCAL_TO_HWIRQ(intr));
else
- do_IRQ(irq_find_mapping(gic_irq_domain,
- GIC_LOCAL_TO_HWIRQ(intr)));
+ do_domain_IRQ(gic_irq_domain,
+ GIC_LOCAL_TO_HWIRQ(intr));
}
}

diff --git a/drivers/irqchip/irq-pic32-evic.c b/drivers/irqchip/irq-pic32-evic.c
index 34c4b4ffacd1..1d9bb28d13e5 100644
--- a/drivers/irqchip/irq-pic32-evic.c
+++ b/drivers/irqchip/irq-pic32-evic.c
@@ -42,11 +42,10 @@ static void __iomem *evic_base;

asmlinkage void __weak plat_irq_dispatch(void)
{
- unsigned int irq, hwirq;
+ unsigned int hwirq;

hwirq = readl(evic_base + REG_INTSTAT) & 0xFF;
- irq = irq_linear_revmap(evic_irq_domain, hwirq);
- do_IRQ(irq);
+ do_domain_IRQ(evic_irq_domain, hwirq);
}

static struct evic_chip_data *irqd_to_priv(struct irq_data *data)
--
2.30.2