[PATCH] virtinst: use 'host-passthrough' as default 'host' on AArch64

[Liang Yan]

Thanks for the reply.

On 4/7/20 9:28 AM, Daniel P. Berrangé wrote:
> On Tue, Apr 07, 2020 at 08:01:50AM -0400, Liang Yan wrote:
>> Thanks for the input.
>>
>> On 4/7/20 3:54 AM, Andrea Bolognani wrote:
>>> On Mon, 2020-04-06 at 16:51 -0400, Liang Yan wrote:
>>>> virt-install already uses 'host-passthrough' as default when no setup
>>>> for cmline '--cpu'. However, it will still use 'host-model' when comes
>>>> with '-cpu host'. This will be a problem for aarch64 platfrom as
>>>> 'host-model' for aarch64 kvm domain on aarch64 host is not supported yet.
>>>
>>> virt-install's --cpu host maps to libvirt's
>>>
>>>   <cpu mode='host-model'/>
>>>
>>> while virt-install's --cpu host-passthrough maps to libvirt's
>>>
>>>   <cpu mode='host-passthrough'/>
>>>
>>> These semantics are not architecture dependent and, while the choice
>>> of name is a bit unfortunate considering that QEMU's -cpu host and
>>> virt-install's --cpu host have different meanings, I think they're
>>> completely unambiguous and reasonably documented, and we should not
>>> mess with them.
>>>
>>
>>
>> virt-install supports both "host","host-mdoel" and "host-passthrough",
>> "--cpu host" is mapped to "host-model" based on "cli:det_model_b",
>> however if you check the default setup in "cpu"set_defaults", it has
>> different configuration. Btw, it has different setup for different
>> architecture already.  Nova also has different setup for aarch64 in my
>> defense.
>>
>> https://opendev.org/openstack/nova/commit/8bc7b950b7c0a3c80cdd120fe4df97c14848c344
>>
>>
>>
>> I agree we could document this situation at least. It does block our
>> aarch64 tests while it is ok for x86_64.
> 
> That is a bug in the tests - they shouldn't be trying to use a feature
> which doesn't make sense for that arch,
>

If "--cpu host" means "--cpu host-model" and we could setup "--cpu
host-model" manually and there is situation could not support "--cpu
host", maybe we just use "--cpu host-model" instead? Just personally
thought "host" "host-model" and "host-passthrough" are a little bit
confusion here. We may improve the error message with more hints at least.

Best,
Liang


> 
> Regards,
> Daniel
>