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genirq: Provide interrupt injection mechanism

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Error injection mechanisms need a half ways safe way to inject interrupts as
invoking generic_handle_irq() or the actual device interrupt handler
directly from e.g. a debugfs write is not guaranteed to be safe.

On x86 generic_handle_irq() is unsafe due to the hardware trainwreck which
is the base of x86 interrupt delivery and affinity management.

Move the irq debugfs injection code into a separate function which can be
used by error injection code as well.

The implementation prevents at least that state is corrupted, but it cannot
close a very tiny race window on x86 which might result in a stale and not
serviced device interrupt under very unlikely circumstances.

This is explicitly for debugging and testing and not for production use or
abuse in random driver code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de
This commit is contained in:
Thomas Gleixner
2020-03-06 14:03:47 +01:00
parent da90921acc
commit acd26bcf36
6 changed files with 61 additions and 37 deletions
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53
kernel/irq/resend.c
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@@ -91,7 +91,7 @@ static int irq_sw_resend(struct irq_desc *desc)
*
* Is called with interrupts disabled and desc->lock held.
*/
int check_irq_resend(struct irq_desc *desc)
int check_irq_resend(struct irq_desc *desc, bool inject)
{
int err = 0;
@@ -108,7 +108,7 @@ int check_irq_resend(struct irq_desc *desc)
if (desc->istate & IRQS_REPLAY)
return -EBUSY;
if (!(desc->istate & IRQS_PENDING))
if (!(desc->istate & IRQS_PENDING) && !inject)
return 0;
desc->istate &= ~IRQS_PENDING;
@@ -122,3 +122,52 @@ int check_irq_resend(struct irq_desc *desc)
desc->istate |= IRQS_REPLAY;
return err;
}
#ifdef CONFIG_GENERIC_IRQ_INJECTION
/**
* irq_inject_interrupt - Inject an interrupt for testing/error injection
* @irq: The interrupt number
*
* This function must only be used for debug and testing purposes!
*
* Especially on x86 this can cause a premature completion of an interrupt
* affinity change causing the interrupt line to become stale. Very
* unlikely, but possible.
*
* The injection can fail for various reasons:
* - Interrupt is not activated
* - Interrupt is NMI type or currently replaying
* - Interrupt is level type
* - Interrupt does not support hardware retrigger and software resend is
* either not enabled or not possible for the interrupt.
*/
int irq_inject_interrupt(unsigned int irq)
{
struct irq_desc *desc;
unsigned long flags;
int err;
/* Try the state injection hardware interface first */
if (!irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, true))
return 0;
/* That failed, try via the resend mechanism */
desc = irq_get_desc_buslock(irq, &flags, 0);
if (!desc)
return -EINVAL;
/*
* Only try to inject when the interrupt is:
* - not NMI type
* - activated
*/
if ((desc->istate & IRQS_NMI) || !irqd_is_activated(&desc->irq_data))
err = -EINVAL;
else
err = check_irq_resend(desc, true);
irq_put_desc_busunlock(desc, flags);
return err;
}
EXPORT_SYMBOL_GPL(irq_inject_interrupt);
#endif