Re: [Qemu-arm] [Qemu-devel] [PATCH] ARM: KVM: Enable in-kernel timers with user space gic

[Andrew Jones]

On Tue, Jun 27, 2017 at 03:59:51PM +0200, Andrew Jones wrote:
> On Tue, Jun 27, 2017 at 03:00:10PM +0200, Alexander Graf wrote:
> > > > +        /* XXX PMU IRQ is missing */
> > > 
> > > So I was wondering why you chose not to wire up the PMU in order to finish
> > 
> > Because the PMU IRQ is only available from the machine file, so it'll need
> > some more plumbing to get the qemu_irq object available from kvm.c.
> 
> OK, I just wrote a patch based on this patch for the PMU and will post it
> in a second.
> 
> > 
> > > this off, since I knew KVM has commit 3dbbdf78636e "KVM: arm/arm64: Report
> > > PMU overflow interrupts to userspace irqchip", which I presume should
> > > allow the PMU to work too. However, attempting to start a guest with
> > > -machine virt,accel=kvm,kernel-irqchip=off -cpu host,pmu=on doesn't 
> > > provide
> > > it a PMU. AFAICT, that's only because KVM still has
> > > 
> > >          /*
> > >           * We currently require an in-kernel VGIC to use the PMU 
> > > emulation,
> > >           * because we do not support forwarding PMU overflow interrupts 
> > > to
> > >           * userspace yet.
> > >           */
> > >          if (!irqchip_in_kernel(vcpu->kvm) || 
> > > !vgic_initialized(vcpu->kvm))
> > >                  return -ENODEV;
> > > 
> > > in kvm_arm_pmu_v3_init(). Anyone know why that wasn't removed with
> > > 3dbbdf78636e?

Eh, I missed a2befacf5094 "KVM: arm64: Allow creating the PMU without the
in-kernel GIC", which is still in kvmarm/queue, not yet in Linus master.
I'll have to revisit the QEMU patch I wrote to make sure it still makes
sense.

drew