Re: [RFC PATCH 4/4] KVM: x86: Add support for local interrupt requests from userspace

[Paolo Bonzini <pbonzini@redhat.com>]

On 13/05/2015 03:47, Steve Rutherford wrote:
> In order to enable userspace PIC support, the userspace PIC needs to
> be able to inject local interrupt requests.
> 
> This adds the ioctl KVM_REQUEST_LOCAL_INTERRUPT and kvm exit
> KVM_EXIT_GET_EXTINT.
> 
> The vm ioctl KVM_REQUEST_LOCAL_INTERRUPT makes a KVM_REQ_EVENT request
> on the BSP, which causes the BSP to exit to userspace to fetch the
> vector of the underlying external interrupt, which the BSP then
> injects into the guest. This matches the PIC spec, and is necessary to
> boot Windows.
> 
> Boots and passes the KVM unit tests on intel x86 with the
> PIC/PIT/IOAPIC in userspace (under a non-QEMU VMM). Boots and passes
> the KVM unit tests under normal conditions as well.
> 
> SVM support and device assignment are untested with this feature
> enabled, but testing for both is in the works.
> 
> Compiles for ARM/x86/PPC.

This may be ENOCOFFEE, but where is extint.vector read?

Could you use KVM_INTERRUPT to set KVM_REQUEST_LOCAL_INTERRUPT _and_ the
interrupt vector at the same time?  This is exactly the logic that is
used for !irqchip, and it should work for the EXTINT case as well.

Paolo