Re: [PATCH] KVM: x86: always exit on EOIs for interrupts listed in the IOAPIC redir table

Paolo Bonzini
2014-08-07T06:13:32Z

Il 07/08/2014 03:31, Zhang, Yang Z ha scritto:
> Let me give an example to see whether my concern is a real problem:
> Guest allocates a vector and set it in IOAPIC entry to deliver
> interrupt. Later it masks the IOAPIC entry(means stop the
> corresponding device) and assign this vector to a MSI device. With
> this patch, even the vector is not used by IOAPIC, but it still set
> eoi exit bitmap unconditionally. The subsequent EOIs to MSI device
> will force vmexit. Could this happen?

Yes, I guess it could. I'm not sure whether it could on Linux or Windows.

> I think the right fixing is to check the ISR plus TMR to construct
> the eoi exit bitmap.

Do you care enough to propose a patch? :)

Paolo