Re: [PATCH v3 10/11] KVM: arm/arm64: prepare GICv3 emulation to use kvm_io_bus MMIO handling

Marc Zyngier
2015-03-27T07:34:50Z

On Fri, 27 Mar 2015 00:14:12 +0000
Andre Przywara <andre.przywara@arm.com> wrote:

> On 03/26/2015 10:06 PM, Marc Zyngier wrote:
> > On Thu, 26 Mar 2015 14:39:37 +0000
> > Andre Przywara <andre.przywara@arm.com> wrote:
> >
> >> Using the framework provided by the recent vgic.c changes, we
> >> register a kvm_io_bus device on mapping the virtual GICv3 resources.
> >> The distributor mapping is pretty straight forward, but the
> >> redistributors need some more love, since they need to be tagged with
> >> the respective redistributor (read: VCPU) they are connected with.
> >> We use the kvm_io_bus framework to register one devices per VCPU.
> >>
> >> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> >> ---
> >> include/kvm/arm_vgic.h | 1 +
> >> virt/kvm/arm/vgic-v3-emul.c | 39 ++++++++++++++++++++++++++++++++++++++-
> >> 2 files changed, 39 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> >> index 4523984..d6705f4 100644
> >> --- a/include/kvm/arm_vgic.h
> >> +++ b/include/kvm/arm_vgic.h
> >> @@ -252,6 +252,7 @@ struct vgic_dist {
> >>
> >> struct vgic_vm_ops vm_ops;
> >> struct vgic_io_device dist_iodev;
> >> + struct vgic_io_device *redist_iodevs;
> >> };
> >>
> >> struct vgic_v2_cpu_if {
> >> diff --git a/virt/kvm/arm/vgic-v3-emul.c b/virt/kvm/arm/vgic-v3-emul.c
> >> index 2f03a36..eb1a797 100644
> >> --- a/virt/kvm/arm/vgic-v3-emul.c
> >> +++ b/virt/kvm/arm/vgic-v3-emul.c
> >> @@ -758,6 +758,9 @@ static int vgic_v3_map_resources(struct kvm *kvm,
> >> {
> >> int ret = 0;
> >> struct vgic_dist *dist = &kvm->arch.vgic;
> >> + gpa_t rdbase = dist->vgic_redist_base;
> >> + struct vgic_io_device *iodevs = NULL;
> >> + int i;
> >>
> >> if (!irqchip_in_kernel(kvm))
> >> return 0;
> >> @@ -783,7 +786,41 @@ static int vgic_v3_map_resources(struct kvm *kvm,
> >> goto out;
> >> }
> >>
> >> - kvm->arch.vgic.ready = true;
> >> + ret = vgic_register_kvm_io_dev(kvm, dist->vgic_dist_base,
> >> + GIC_V3_DIST_SIZE, vgic_v3_dist_ranges,
> >> + -1, &dist->dist_iodev);
> >
> >> + if (ret)
> >> + goto out;
> >> +
> >> + iodevs = kcalloc(dist->nr_cpus, sizeof(iodevs[0]), GFP_KERNEL);
> >> + if (!iodevs) {
> >> + ret = -ENOMEM;
> >> + goto out_unregister;
> >> + }
> >> +
> >> + for (i = 0; i < dist->nr_cpus; i++) {
> >> + ret = vgic_register_kvm_io_dev(kvm, rdbase,
> >> + SZ_128K, vgic_redist_ranges,
> >> + i, &iodevs[i]);
> >
> > This looks really weird. You seems to be mapping all redistributors at
> > the same IPA. Have you actually tested this with an SMP guest?
>
> But the patch continues:
>
> + if (ret)
> + goto out_unregister;
> + rdbase += GIC_V3_REDIST_SIZE;
>
> Is that too confusing to re-use the rdbase variable? The spec speaks of
> RD_base for each redistributor, so that seemed sane to me.
> Shall I add a comment or use "rdbase + i * GIC_V3_REDIST_SIZE" for clarity?

That would have been nicer, but let's face the harsh truth: I can't
read, ignore me (well, for this time only ;-).

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

M.
--
Jazz is not dead. It just smells funny.