Re: [PATCH] kvm: arm64: vgic: fix hyp panic with 64k pages on juno platform

[Joel Schopp <joel.schopp@amd.com>]

>>>> I can't think of any way of determining whether a particular
>>>> system gets this right or wrong automatically, which suggests
>>>> perhaps we need to allow the device tree to specify that the
>>>> GICV is 64k-page-safe...
>>> When we support such systems, I also think we'll need a device-tree change.
>>> My main concern right now is stopping the ability to hose the entire machine
>>> by trying to instantiate a virtual GIC.
>> ...I don't see how your patch prevents instantiating a VGIC
>> and hosing the machine on a system where the 64K
>> with the GICV registers in it goes
>>  [GICV registers] [machine blows up if you read this]
>>  0K                      8K                                             64K
> True, if such a machine existed, then this patch wouldn't detect it. I don't
> think we support anything like that in mainline at the moment, but the
> following additional diff should solve the problem, no?
>
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index fa9a95b3ed19..476d3bf540a8 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -1539,6 +1539,14 @@ int kvm_vgic_hyp_init(void)
>                 goto out_unmap;
>         }
>  
> +       if (!PAGE_ALIGNED(resource_size(&vcpu_res))) {
> +               kvm_err("GICV size 0x%llx not a multiple of page size 0x%lx\n",
> +                       (unsigned long long)resource_size(&vcpu_res),
> +                       PAGE_SIZE);
> +               ret = -ENXIO;
> +               goto out_unmap;
> +       }
> +
>         vgic_vcpu_base = vcpu_res.start;
>  
>         kvm_info("%s@%llx IRQ%d\n", vgic_node->name,
This would break with my SOC device tree which looks like this.  Note
this device tree works just fine without checks.

    gic: interrupt-controller@e1101000 {
        compatible = "arm,gic-400-v2m";
        #interrupt-cells = <3>;
        #address-cells = <0>;
        interrupt-controller;
        msi-controller;
        reg = <0x0 0xe1110000 0 0x1000>, /* gic dist */
              <0x0 0xe112f000 0 0x2000>, /* gic cpu */
              <0x0 0xe114f000 0 0x2000>, /* gic virtual ic*/
              <0x0 0xe116f000 0 0x2000>, /* gic virtual cpu*/
              <0x0 0xe1180000 0 0x1000>; /* gic msi */
        interrupts = <1 8 0xf04>;
    };