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

Andre Przywara
2015-03-27T00:10:14Z

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?

Cheers,
Andre.