Hi all,
This series introduces support for running GICv3 guests on GICv5 hosts
by leveraging the GICv5 legacy compatibility feature
(FEAT_GCIE_LEGACY). The main motivation is to enable existing GICv3
VMs on GICv5 system without VM or VMM modifications - things should
work out of the box.
The changes are focused on two main areas:
KVM GIC support: Enabling detection of a GICv5 host and
configuring it to support GICv3 guests.
IRQ chip support: Ensuring forwarded PPIs behave consistently with
GICv3 expectations.
Summary of the patches:
Ensure injected guest interrupts behave correctly by deferring
deactivation to the guest, matching GICv3-native behavior.
Set up the necessary GIC capabilities to advertise
FEAT_GCIE_LEGACY to KVM.
Add missing system register required for enabling GICv3 compat
mode from EL2.
Enable full support for running GICv3 VMs on a GICv5 host when
compat mode is present, covering VHE, nVHE, and protected KVM
configurations (excluding nested virt).
Introduce a probe routine to enable GICv5 when FEAT_GCIE_LEGACY is
detected. This consumes the gic_kvm_info populated earlier.
This support has been co-developed with T.Hayes, indicated with
Co-authored-by tags.
This series is based and dependent on [PATCH v6 00/31] Arm GICv5: Host
driver implementation [1].
Feedback welcome!
Thanks,
Sascha
[1] https://lore.kernel.org/all/20250626-gicv5-host-v6-0-48e046af4642@kernel.org/
---
Changes in v2:
- Switched to a lazy-disable approach for compat mode
- Merged compat mode enable into __vgic_v3_restore_vmcr_aprs
- Moved to using GICV5_CPUIF cpucap, where possible
- Cleaned up helper functions
- Added Reviewed-by tag
- Link to v1: https://lore.kernel.org/all/20250620160741.3513940-1-sascha.bischoff@arm.com/
---
Sascha Bischoff (5):
irqchip/gic-v5: Skip deactivate for forwarded PPI interrupts
irqchip/gic-v5: Populate struct gic_kvm_info
arm64/sysreg: Add ICH_VCTLR_EL2
KVM: arm64: gic-v5: Support GICv3 compat
KVM: arm64: gic-v5: Probe for GICv5
arch/arm64/kvm/Makefile | 3 +-
arch/arm64/kvm/hyp/vgic-v3-sr.c | 51 +++++++++++++++++++++-----
arch/arm64/kvm/sys_regs.c | 10 +++++-
arch/arm64/kvm/vgic/vgic-init.c | 9 +++--
arch/arm64/kvm/vgic/vgic-v5.c | 52 +++++++++++++++++++++++++++
arch/arm64/kvm/vgic/vgic.h | 13 +++++++
arch/arm64/tools/sysreg | 6 ++++
drivers/irqchip/irq-gic-v5.c | 50 ++++++++++++++++++++++++++
include/kvm/arm_vgic.h | 6 +++-
include/linux/irqchip/arm-vgic-info.h | 4 +++
10 files changed, 191 insertions(+), 13 deletions(-)
create mode 100644 arch/arm64/kvm/vgic/vgic-v5.c
--
2.34.1