Commit 1fee9db9 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

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



Since d4a45c68 ("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: default avatarGuenter Roeck <linux@roeck-us.net>
Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
[maz: add dependency on CONFIG_IRQ_DOMAIN after report from the kernelci bot]
Signed-off-by: default avatarMarc 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
Link: https://lore.kernel.org/r/20210706110647.3979002-1-maz@kernel.org
parent 0e3c1f30

arch/mips/include/asm/irq.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

arch/mips/kernel/irq.c

+16 −0
Original line number Diff line number Diff line
@@ -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 +108,18 @@ void __irq_entry do_IRQ(unsigned int irq) 
	irq_exit();

}



#ifdef CONFIG_IRQ_DOMAIN

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();

}

#endif

drivers/irqchip/irq-mips-cpu.c

+6 −4
Original line number Diff line number Diff line
@@ -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);

	}

}

drivers/irqchip/irq-mips-gic.c

+4 −4
Original line number Diff line number Diff line
@@ -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));

	}

}

drivers/irqchip/irq-pic32-evic.c

+2 −3
Original line number Diff line number Diff line
@@ -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)