Re: [Qemu-devel] [RFC v2 3/3] virt: Check KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 for smp_cpus > 256

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 11 Sep 2019 at 16:51, Eric Auger <eric.auger@redhat.com> wrote:
>
> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
> for ARM. The actual capability to instantiate more than 256 vcpus
> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
> a single KVM IO device instead of 2.
>
> So let's check this capability when attempting to use more than 256
> vcpus.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/arm/virt.c        |  4 ++++
>  target/arm/kvm.c     | 21 +++++++++++++++++++++
>  target/arm/kvm_arm.h | 15 +++++++++++++++
>  3 files changed, 40 insertions(+)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 0d1629ccb3..465e3140f7 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1575,6 +1575,10 @@ static void machvirt_init(MachineState *machine)
>          virt_max_cpus = GIC_NCPU;
>      }
>
> +    if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
> +        exit(1);
> +    }
> +

Is there really no place to put this check in common code?

thanks
-- PMM