[PATCH v3 0/4] KVM: arm64: Add attribute to control GICD_TYPER2.nASSGIcap

Raghavendra Rao Ananta
2025-06-13T15:52:43Z

A shortcoming of the GIC architecture is that there's an absolute limit on
the number of vPEs that can be tracked by the ITS. It is possible that
an operator is running a mix of VMs on a system, only wanting to provide
a specific class of VMs with hardware interrupt injection support.

The series introduces KVM_DEV_ARM_VGIC_FEATURE_nASSGIcap vGIC attribute to allow
the userspace to control GICD_TYPER2.nASSGIcap (GICv4.1) on a per-VM basis.

v1: https://lore.kernel.org/kvmarm/20250514192159.1751538-1-rananta@google.com/

v1 -> v2: https://lore.kernel.org/all/20250531012545.709887-1-oliver.upton@linux.dev/
- Drop all use of GICv4 in the UAPI and KVM-internal helpers in favor
of nASSGIcap. This changes things around to model a guest feature,
not a host feature.

- Consolidate UAPI into a single attribute and expect userspace to use
to read the attribute for discovery, much like we do with the ID
registers

- Squash documentation together with implementation

- Clean up maintenance IRQ attribute handling, which I ran into as part
of reviewing this series

v2 -> v3:
- Update checks in vgic-v3.c and vgic-v4.c to also include nASSGIcap (via
vgic_supports_direct_sgis()) that's configured by the userspace. (Oliver)

Oliver Upton (2):
KVM: arm64: Disambiguate support for vSGIs v. vLPIs
KVM: arm64: vgic-v3: Consolidate MAINT_IRQ handling

Raghavendra Rao Ananta (2):
KVM: arm64: Introduce attribute to control GICD_TYPER2.nASSGIcap
KVM: arm64: selftests: Add test for nASSGIcap attribute

.../virt/kvm/devices/arm-vgic-v3.rst | 29 ++++++
arch/arm64/include/uapi/asm/kvm.h | 3 +
arch/arm64/kvm/vgic/vgic-init.c | 7 +-
arch/arm64/kvm/vgic/vgic-kvm-device.c | 88 +++++++++++++------
arch/arm64/kvm/vgic/vgic-mmio-v3.c | 24 +++--
arch/arm64/kvm/vgic/vgic-v3.c | 5 +-
arch/arm64/kvm/vgic/vgic-v4.c | 6 +-
arch/arm64/kvm/vgic/vgic.c | 4 +-
arch/arm64/kvm/vgic/vgic.h | 7 ++
include/kvm/arm_vgic.h | 3 +
tools/testing/selftests/kvm/arm64/vgic_init.c | 41 +++++++++
11 files changed, 176 insertions(+), 41 deletions(-)

base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
--
2.50.0.rc2.692.g299adb8693-goog