KVM: arm64: GICv3: nv: Resync LRs/VMCR/HCR early for better MI emulation

The current approach to nested GICv3 support is to not do anything
while L2 is running, wait a transition from L2 to L1 to resync
LRs, VMCR and HCR, and only then evaluate the state to decide
whether to generate a maintenance interrupt.

This doesn't provide a good quality of emulation, and it would be
far preferable to find out early that we need to perform a switch.

Move the LRs/VMCR and HCR resync into vgic_v3_sync_nested(), so
that we have most of the state available. As we turning the vgic
off at this stage to avoid a screaming host MI, add a new helper
vgic_v3_flush_nested() that switches the vgic on again. The MI can
then be directly injected as required.

Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://msgid.link/20251120172540.2267180-35-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index dbf16a9f6772..76ce2b94bd97 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -77,6 +77,7 @@ DECLARE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
 int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu);
 
 u64 __gic_v3_get_lr(unsigned int lr);
+void __gic_v3_set_lr(u64 val, int lr);
 
 void __vgic_v3_save_state(struct vgic_v3_cpu_if *cpu_if);
 void __vgic_v3_restore_state(struct vgic_v3_cpu_if *cpu_if);