KVM: arm64: gic-v5: Communicate userspace-driveable PPIs via a UAPI

KVM: arm64: gic-v5: Communicate userspace-driveable PPIs via a UAPI

GICv5 systems will likely not support the full set of PPIs. The
presence of any virtual PPI is tied to the presence of the physical
PPI. Therefore, the available PPIs will be limited by the physical
host. Userspace cannot drive any PPIs that are not implemented.

Moreover, it is not desirable to expose all PPIs to the guest in the
first place, even if they are supported in hardware. Some devices,
such as the arch timer, are implemented in KVM, and hence those PPIs
shouldn't be driven by userspace, either.

Provided a new UAPI:
  KVM_DEV_ARM_VGIC_GRP_CTRL => KVM_DEV_ARM_VGIC_USERPSPACE_PPIs

This allows userspace to query which PPIs it is able to drive via
KVM_IRQ_LINE.

Additionally, introduce a check in kvm_vm_ioctl_irq_line() to reject
any PPIs not in the userspace mask.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260319154937.3619520-40-sascha.bischoff@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>