DOR : Example for injecting the interrupt to the guest

[Ajith Chandran <aji007-BoNl9JPmOHUAvxtiuMwx3w@public.gmane.org>]

Hello Dor,

Can you please point to an example that injects interrupts via userspace ?

I am running QNX as Guest and Linux as Host. One of my QNX application (Guest application), expects an interrupt from the Hardware. 

Now as I understand this, I need to write a driver on the host side to get the interrupt and somehow inject the interrupt to guest OS. But I am not sure how to signal the KVM about the arrival of interrupt, without breaking anything.

Ghaskins, suggested your name in kvm-irc. I have pasted relevant part of it for your reference.

Your early response will be highly appreciated,

Thanking you 

Aji

10:36 < aji003> the virtual driver is a part of kvm...and so it runs in the host
10:36 < ghaskins> ok, so yes you are correct
10:36 < ghaskins> the host side would know the real vector of the physical device and would be registered in the host IDT
10:36 < aji003> By virtual driver I mean, the driver I have developed so that the guest app can interact with the physical hardware
10:36 < ghaskins> it would then probably do something like proxy the interrupts into the guest
10:37 < ghaskins> ok, i understand you now
10:37 < ghaskins> so your proxy/virtual driver would get the real interrupt...you then would want to inject it into the guest as a virtual interrupt
10:37 < aji003> yes thatz what I wanted to do..sorry if i confused you
10:38 < ghaskins> no problem..its clear now
10:38 < ghaskins> so I assume you already know how to write your virtual driver and register it with linux with the write vector, etc
10:38 < ghaskins> ?
10:38 < ghaskins> and now you just want to know how to inject the interrupt to the guest
10:38 < aji003> I did it for I/O and memory mapping, but I am not sure about how to do for interrupt
10:41 < ghaskins> so are we on the same page:  your proxy will handle the real vector?
10:42 < aji003> KVM has a virtualised 8259 driver
10:43 < ghaskins> yeah, but that code is also in flux right now too
10:43 < ghaskins> as of right now, the interrupt infrastructure is all in userspace/QEMU
10:43 < ghaskins> its in the process of being moved down into the kernel
10:44 < ghaskins> at that point it will be much easier to inject interrupts from the kernel, which it sounds like you might need to do
10:44 < aji003> ok
10:44 < aji003> so with qemu, itz not possible ?
10:44 < ghaskins> but as a high level overview, there are emulated 8259s and APICs
10:45 < ghaskins> well, it should be possible...its just more difficult
10:45 < aji003> ok..
10:45 < ghaskins> I think Dor has written a driver that utilizes the userspace interrupt stuff as you would need to
< ghaskins> I think Dor has written a driver that utilizes the userspace interrupt stuff as you would need to
10:45 < aji003> Dor ?
10:46 < aji003> I am quite new to linux and KVM 
10:46 < ghaskins> He's one of the Qumranet guys...if he is not here on IRC just hit the list
10:46 < ghaskins> kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
10:46 < ghaskins> he can probably point you to an example of his that injects interrupts via userspace
10:46 < aji003> ok
10:47 < ghaskins> and it will all get a little simplified in a few weeks when the in-kernel stuff merges
10:47 < aji003> Thanks ghaskins

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