On Tue, Jun 03 2014 at 2:25:10 pm BST, "Bharat.Bhushan@xxxxxxxxxxxxx" <Bharat.Bhushan@xxxxxxxxxxxxx> wrote: >> -----Original Message----- >> From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx] >> Sent: Tuesday, June 03, 2014 5:40 PM >> To: Bhushan Bharat-R65777 >> Cc: Mathew Li; kvmarm@xxxxxxxxxxxxxxxxxxxxx >> Subject: Re: Few general questions on kvm-arm >> >> On Tue, Jun 03 2014 at 12:10:28 pm BST, "Bharat.Bhushan@xxxxxxxxxxxxx" >> <Bharat.Bhushan@xxxxxxxxxxxxx> wrote: >> >> > 2. Looking at the code in virt/kvm/arm/vgic.c, it looks like we use >> >> > maintenance interrupt to update our in-memory data structures when >> >> > guest EOIs the interrupt. That would mean, we would exit the VM >> >> > every time guest does an EOI. Is that correct? >> >> >> >> Only when we use level interrupts. >> > >> > Do you mean that it exit on EOI for level interrupt and not for >> > edge/msi interrupts? >> >> Exactly. >> >> > Can you please explain how vgic send next available interrupt of lower >> > or same priority if not exit on EOI for msi/edge interrupt? >> >> Look at point 4 of Mathew's description. When injecting the >> interrupt, you kick >> the vcpu to force it to reload its state. >> >> Additionally, if you have more pending interrupts than your list >> registers can contain, you set the underflow trigger for the >> maintainance interrupt, > > Let us take an example; Say There are 2 interrupts which needed to be > injected to guest. > - kick vcpu > - reload state of vcpu and now guest can see 2 interrupts. > - Guest might disable the interrupt while handling above mentioned interrupt > - 3rd interrupt requires to be injected to guest. > - host does kick vcpu > - Will the 3rd interrupt will be seen to guest now? Or is this the > point where we set a underflow trigger? If there is space left in the list registers and the the interrupt is not disabled (I cannot really tell from your description above), then it will be visible by the guest. > - Now when guest re-enable interrupt then it will exit to kvm and kvm > will reload new state? Assuming your talking about enabling/disabling specific interrupts, then yes. We always trap on GICD access. >> resulting >> in an exit when you can reload new pending interrupts. > > What do we mean by "exit when you can reload new pending interrupts", > I mean how we know that now we should reload new state ? Because that's what the vgic code does: its very job is to track interrupts and inject what needs to be injected. At that stage, I suggest you take a look at the code and become familiar with how it works. Thanks, M. -- Jazz is not dead. It just smells funny. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
