> On 9 Jun 2018, at 12:06, Christoffer Dall <christoffer.dall@xxxxxxx> wrote:
>
>> On Fri, Jun 01, 2018 at 05:06:28PM +0200, Ard Biesheuvel wrote:
>> When booting a 64 KB pages kernel on a ACPI GICv3 system that
>> implements support for v2 emulation, the following warning is
>> produced
>>
>> GICV size 0x2000 not a multiple of page size 0x10000
>>
>> and support for v2 emulation is disabled, preventing GICv2 VMs
>> from being able to run on such hosts.
>>
>> The reason is that vgic_v3_probe() performs a sanity check on the
>> size of the window (it should be a multiple of the page size),
>> while the ACPI MADT parsing code hardcodes the size of the window
>> to 8 KB. This makes sense, considering that ACPI does not bother
>> to describe the size in the first place, under the assumption that
>> platforms implementing ACPI will follow the architecture and not
>> put anything else in the same 64 KB window.
>
> Does the architecture actually say that anywhere?
>
>>
>> So let's just drop the sanity check altogether, and assume that
>> the window is at least 64 KB in size.
>
> This could obviously be dangerous if broken systems actually exist.
> Marc may know more about that than me. An alternative would be to
> modify the ACPI code to assume max(8 KB, page size) instead, and/or a
> command line parameter to override this check.
>
> That said, I'm not directly opposed to this patch, but I'll let Marc
> have a look as well.
>
This approach was actually Marc’s idea, and he already applied the patch to the queue branch afaik.
>
>>
>> Fixes: 909777324588 ("KVM: arm/arm64: vgic-new: vgic_init: implement kvm_vgic_hyp_init")
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> ---
>> virt/kvm/arm/vgic/vgic-v3.c | 5 -----
>> 1 file changed, 5 deletions(-)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
>> index bdcf8e7a6161..72fc688c3e9d 100644
>> --- a/virt/kvm/arm/vgic/vgic-v3.c
>> +++ b/virt/kvm/arm/vgic/vgic-v3.c
>> @@ -552,11 +552,6 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
>> pr_warn("GICV physical address 0x%llx not page aligned\n",
>> (unsigned long long)info->vcpu.start);
>> kvm_vgic_global_state.vcpu_base = 0;
>> - } else if (!PAGE_ALIGNED(resource_size(&info->vcpu))) {
>> - pr_warn("GICV size 0x%llx not a multiple of page size 0x%lx\n",
>> - (unsigned long long)resource_size(&info->vcpu),
>> - PAGE_SIZE);
>> - kvm_vgic_global_state.vcpu_base = 0;
>> } else {
>> kvm_vgic_global_state.vcpu_base = info->vcpu.start;
>> kvm_vgic_global_state.can_emulate_gicv2 = true;
>> --
>> 2.17.0
>>
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