USB HID driver fails to recognize input devices

Julian Stecklina js at ...14...
Fri Jul 20 21:22:37 CEST 2012

Am Mittwoch, den 18.07.2012, 11:44 +0200 schrieb Udo Steinberg:
> An active IOMMU will only let interrupt vectors through that have been
> explicitly whitelisted by the hypervisor. Applications request an interrupt
> by means of the assign_gsi hypercall and also specify which CPU they want
> the interrupt routed to. This must be done for any interrupt (IOAPIC or MSI).

One quick addition to this: If you guys implement that, be sure to test
it on a box that actually has Interrupt Remapping support. The kernel
will hide the difference (it magically returns the correct MSI
address/value pair to program), but if it works on a box with Interrupt
Remapping support, you are sure that you did everything correctly.

Udo, is there an easy way to figure out, if a system supports Interrupt
Remapping short of looking into ACPI tables?

> (I'm thinking about adding some code to the hypervisor, causing sem_down to
> fail on an interrupt semaphore unless the interrupt has been configured
> using assign_gsi.)

+1 from me. That would cause broken code to fail early.

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