x86/i8259: Mark legacy PIC interrupts with IRQ_LEVEL

Baoquan reported that after triggering a crash the subsequent crash-kernel
fails to boot about half of the time. It triggers a NULL pointer
dereference in the periodic tick code.

This happens because the legacy timer interrupt (IRQ0) is resent in
software which happens in soft interrupt (tasklet) context. In this context
get_irq_regs() returns NULL which leads to the NULL pointer dereference.

The reason for the resend is a spurious APIC interrupt on the IRQ0 vector
which is captured and leads to a resend when the legacy timer interrupt is
enabled. This is wrong because the legacy PIC interrupts are level
triggered and therefore should never be resent in software, but nothing
ever sets the IRQ_LEVEL flag on those interrupts, so the core code does not
know about their trigger type.

Ensure that IRQ_LEVEL is set when the legacy PCI interrupts are set up.

Fixes: a4633adcdbc1 ("[PATCH] genirq: add genirq sw IRQ-retrigger")
Reported-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Baoquan He <bhe@redhat.com>
Link: https://lore.kernel.org/r/87mt6rjrra.ffs@tglx

diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c
index 3aa5304200c5073d380ddcbe240d49b09129fab2..4d8aff05a509ec4ca413b08e3d26ca812f5d94e7 100644 (file)
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -114,6 +114,7 @@ static void make_8259A_irq(unsigned int irq)
        disable_irq_nosync(irq);
        io_apic_irqs &= ~(1<<irq);
        irq_set_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
+       irq_set_status_flags(irq, IRQ_LEVEL);
        enable_irq(irq);
        lapic_assign_legacy_vector(irq, true);
 }

diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index beb1bada1b0ab2da5c5bd6d6b6ddde8ee6245d4b..c683666876f1c7026acf5b4d63b93381181e1801 100644 (file)
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -65,8 +65,10 @@ void __init init_ISA_irqs(void)
 
        legacy_pic->init(0);
 
-       for (i = 0; i < nr_legacy_irqs(); i++)
+       for (i = 0; i < nr_legacy_irqs(); i++) {
                irq_set_chip_and_handler(i, chip, handle_level_irq);
+               irq_set_status_flags(i, IRQ_LEVEL);
+       }
 }
 
 void __init init_IRQ(void)