[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen: do not unmask disabled IRQ on eoi.
This prevents a guest from being able to trigger an interrupt storm in dom0 rendering it inoperable. In particular this effects event channels delivered to userspace by the /dev/xen/evtchn driver which uses disable_irq in its interupt handler to prevent further interrupts firing until the interrupt has been handled by the userspace application and it has requested an unmask. Without this patch the event channel is re-enabled immediately after the interrupt handler completes. The issue was introduced by 0672fb44a111 "xen/events: change to using fasteoi". In the specific instance I saw a domU would spin sending console event channel notifications to dom0 because its console ring was full (this behaviour has since been tempered by f3483182666a "xen/hvc: only notify if we actually sent something") but xenconsoled would be unable to run due to the storm and hence the ring would never be drained. I'm not convinced this is the right way to go about this -- there does not seem to be much precedent and I would have expected some sort of generic handling but I cannot see any. Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> --- drivers/xen/events.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/drivers/xen/events.c b/drivers/xen/events.c index 1496ba5..a9b0637 100644 --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -1215,6 +1215,17 @@ int resend_irq_on_evtchn(unsigned int irq) return 1; } +static void eoi_dynirq(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + int evtchn = evtchn_from_irq(irq); + + move_masked_irq(irq); + + if (VALID_EVTCHN(evtchn) & !(desc->status & IRQ_DISABLED)) + unmask_evtchn(evtchn); +} + static void ack_dynirq(unsigned int irq) { int evtchn = evtchn_from_irq(irq); @@ -1408,7 +1419,7 @@ static struct irq_chip xen_dynamic_chip __read_mostly = { .mask = mask_irq, .unmask = unmask_irq, - .eoi = ack_dynirq, + .eoi = eoi_dynirq, .set_affinity = set_affinity_irq, .retrigger = retrigger_irq, }; -- 1.5.6.5 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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