Messages in this thread |  | | Date | Wed, 15 Apr 2015 11:40:08 +0200 | From | Adrian-Ken Rueegsegger <> | Subject | Re: [PATCH] genirq: Only call irq_ack if implemented by chip |
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Hi,
On 04/14/2015 08:00 PM, Thomas Gleixner wrote: > On Tue, 14 Apr 2015, Adrian-Ken Rueegsegger wrote: >> Restore the check if an IRQ chip implements the irq_ack function prior >> to its invocation. Commit 22a49163e90d ("genirq: Provide compat handling >> for chip->ack()") removed the check from handle_edge_irq while keeping >> the check in other call paths. > > How's an edge triggered interrupt without ack supposed to work? > > You are missing to describe which problem you solve.
I am running Linux as a VM on top of the Muen Separation Kernel (SK) [1], where we have implemented PCI device passthrough using VT-d. In this case the hardware interrupt is handled by the SK/hypervisor and injected to Linux.
To support PCI MSI(-X), we register our own platform-specific MSI operations (x86_msi.setup_msi_irqs, etc) and implement an irq_chip that simply provides the irq_mask and irq_unmask operations (by reusing the "regular" mask_msi_irq/unmask_msi_irq).
After encountering a null pointer dereference due to the irq_chip not providing an irq_ack operation, I examined the commit that changed the source of the irq_ack call, noticing that only the check in handle_edge_irq was dropped while the other call sites were kept. As the commit message did not provide me with additional information for that particular fragment of the change, I (prematurely) concluded that it was not intentional.
If it is a prerequisite for IRQ chips to provide the irq_ack operation when used in conjunction with handle_edge_irq, then please ignore my patch. In that case, I will adjust our chip implementation accordingly.
Thanks for your time, Adrian
[1] - http://muen.codelabs.ch/
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