Re: [PATCH v2 2/4] virtio-iommu: Default to bypass during boot

[Cornelia Huck]

On Tue, Feb 08 2022, "Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Feb 08, 2022 at 06:42:57PM +0100, Cornelia Huck wrote:
>> On Thu, Jan 27 2022, Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:
>> 
>> > @@ -988,9 +1025,9 @@ static void virtio_iommu_device_realize(DeviceState 
>> > *dev, Error **errp)
>> >      virtio_add_feature(&s->features, VIRTIO_IOMMU_F_INPUT_RANGE);
>> >      virtio_add_feature(&s->features, VIRTIO_IOMMU_F_DOMAIN_RANGE);
>> >      virtio_add_feature(&s->features, VIRTIO_IOMMU_F_MAP_UNMAP);
>> > -    virtio_add_feature(&s->features, VIRTIO_IOMMU_F_BYPASS);
>> >      virtio_add_feature(&s->features, VIRTIO_IOMMU_F_MMIO);
>> >      virtio_add_feature(&s->features, VIRTIO_IOMMU_F_PROBE);
>> > +    virtio_add_feature(&s->features, VIRTIO_IOMMU_F_BYPASS_CONFIG);
>> 
>> Hm. In the other patch, you say that you don't support cross-version
>> migration (I assume across QEMU versions?)
>
> I missed that ... where does it say this?

In bf447d9b-c039-ccdc-f24f-ab8b56c1b196@redhat.com and follow-ups
(unless I misread that; maybe it's more about this concrete boundary and
not generally?)

>
>> Because changing the feature
>> set will be guest-visible, and would need some compat handling if you
>> plan to support this.