[PATCH 0/4] KVM: arm/arm64: vgic: Virtual interrupt grouping support

Andre Przywara
2018-06-25T09:59:06Z

Hi,

On 24/06/18 23:10, Christoffer Dall wrote:
> This small series addresses a peculiarity of the current VGIC
> implementation, namely that we don't support interrupt grouping.

Nice one and seems straight forward enough.
Just curious: Were there any complaints or even users of FIQs and/or
interrupt grouping?

> KVM either implements a GICv2 without support for the security
> extensions, or a GICv3 with DS=1. For GICv2, on systems without the
> security extensions, group 0 interrupts can be configured to be either
> signalled as FIQs or as IRQs by the VM, whereas group 1 interrupts are
> always IRQs. For GICv3, with DS=1, group 1 interrupts are always IRQs
> and group 0 interrupts are always FIQs, and there is no concept of
> secure vs. non-secure group 1 interrupts when DS=1.
>
> We were treating all interrupts on GICv2 as group 0, but yet telling the
> geust that they were group 1. The first patch changes this behavior,
> which seems to have no effect on no known guests, but still.
>
> The remaining patches introduce proper interrupt grouping support, along
> with MMIO accessors for the VM and userspace to retrieve and set the
> which group SGIs, PPIs, and SPIs belong to. LPIs are always group 1
> interrupts as per the architecture, and there is no way to modify this
> configuration (no IGROUPR registers for LPIs or equivalent ITS
> commands).
>
> Lightly tested on Seattle, TX1, and the foundation model. I've run a
> GICv2 guest on a GICv3 host on the foundation model.

I take it those were regression tests with Linux guests?
Do we have any means of testing this with guests which actually use
different groups or FIQs? Does kvm-unit-tests cover this?

Did you do any tests on 32 bit? I am going to fire up something on my
Midway later today ...

Cheers,
Andre.

> Applies to v4.18-rc1.
>
> Christoffer Dall (4):
> KVM: arm/arm64: GICv2 IGROUPR should read as zero
> KVM: arm/arm64: vgic: Add group field to struct irq
> KVM: arm/arm64: Signal IRQs using their configured group
> KVM: arm/arm64: vgic: Allow VMs to configure interrupt groups
>
> include/kvm/arm_vgic.h | 1 +
> include/linux/irqchip/arm-gic.h | 1 +
> virt/kvm/arm/vgic/vgic-debug.c | 8 ++++---
> virt/kvm/arm/vgic/vgic-init.c | 11 +++++++--
> virt/kvm/arm/vgic/vgic-its.c | 1 +
> virt/kvm/arm/vgic/vgic-mmio-v2.c | 2 +-
> virt/kvm/arm/vgic/vgic-mmio-v3.c | 2 +-
> virt/kvm/arm/vgic/vgic-mmio.c | 38 ++++++++++++++++++++++++++++++++
> virt/kvm/arm/vgic/vgic-mmio.h | 6 +++++
> virt/kvm/arm/vgic/vgic-v2.c | 3 +++
> virt/kvm/arm/vgic/vgic-v3.c | 6 +----
> 11 files changed, 67 insertions(+), 12 deletions(-)
>