[PATCH v2] arm/arm64: KVM: MMIO support for BE guest

[Anup Patel]

On Wed, Oct 30, 2013 at 1:58 PM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On 2013-10-30 01:10, Anup Patel wrote:
>>
>> On Wed, Oct 30, 2013 at 12:19 AM, Marc Zyngier <marc.zyngier at arm.com>
>> wrote:
>>>
>>> Do the necessary byteswap when host and guest have different
>>> views of the universe. Actually, the only case we need to take
>>> care of is when the guest is BE. All the other cases are naturally
>>> handled.
>>
>>
>> You might want to handle the case where we have LE guest on BE host
>> because for ARM64 kernel we might have lot of people interested in
>> running host kernel in BE mode with KVM enabled.
>
>
> What makes you think it is not handled already?

What I understood here is that you are trying to ensure that MMIO data
passed to/from user space (i.e. QEMU or KVMTOOL) is host endian
using vcpu_data_guest_to_host() and vcpu_data_host_to_guest(). This
makes lot of sense for having all combinations of host and guest endianness.

If the above is correct then I see an issue in vcpu_data_guest_to_host() and
vcpu_data_host_to_guest() for LE guest on BE host because this patch does
endianness conversion for BE VCPUs only in vcpu_data_guest_to_host() and
vcpu_data_host_to_guest(). If we have LE guest on BE host then these
functions won't do any endianness conversion.

--
Anup

>
>         M.
> --
> Fast, cheap, reliable. Pick two.