Hi Lukas, On Mon, 04 Oct 2021 11:07:47 +0100, Lukas Jünger <lukas.juenger@xxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > I am trying to run an emulator that uses KVM on arm64 to execute > code. The emulator contains a userspace model of a GICv2 IRQ > controller. The platform that I am running on (n1sdp) has a N1-SDP? My condolences... > GICv3. When I boot Linux in the emulator I run into > gic_check_cpu_features() in drivers/irqchip/irq-gic.c, which taints > the kernel as the host uses system registers to communicate with the > host GICv3. I saw that ICC_SRE_ELx can be used to force MMIO, but > setting this from inside the VM did not work and using KVM_SET_ONE_REG > failed with error. N1-SDP doesn't implement the MMIO interface at all, and our GIC emulation doesn't either. Both are valid implementations. > > Is there a way to use a userspace GICv2 model with KVM on a GICv3 host > without tainting? The tainting happens because you have created a VM with a GICv3 irqchip (at some point, your VMM calls into KVM to create a device with the KVM_DEV_TYPE_ARM_VGIC_V3 attribute). The guest then sees that GICv3 is enabled (ICC_SRE_ELx.SRE==1), and yet you somehow expose a GICv2 to the guest (either via DT or ACPI). That's illegal. If you want a userspace interrupt controller, you need prevent the creation of an in-kernel interrupt controller, which is a change in your VMM or maybe a configuration change. M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
