[libvirt] [PATCH 0/6] RFC: qemu: virtio-{non-}transitional support

[Cole Robinson]

On 01/15/2019 08:30 AM, Andrea Bolognani wrote:
> On Sun, 2019-01-13 at 18:12 -0500, Cole Robinson wrote:
> [...]
>> The main RFC bits here are:
...
> 
>> * The PCI address handling. I just mapped virtio-non-transitional
>>    to imply plain PCI addressing. I think that's all we need but
>>    I'm not positive so I'd appreciate a review of that approach.
> 
> I don't think that's right. Let me fish up a message I wrote a while
> ago summing up interactions between VirtIO devices and PCI (Express)
> slots:
> 
>    http://lists.nongnu.org/archive/html/qemu-devel/2018-11/msg03133.html
> 
> Basically VirtIO 0.9 requires IO space to be available, and 1.0 did
> away with that requirement because PCI Express, unlike conventional
> PCI, allows devices *not* to have IO space.
> 
> So transitional devices, which must work with both 0.9 and 1.0, can
> depend on IO space being available and as such will only work when
> plugged into conventional PCI slots, whereas non-transitional
> devices don't need IO space and can thus be plugged into either
> conventional PCI and PCI Express slots.
> 
> Ultimately, then, transitional (rather than non-transitional)
> devices are the ones that must be forced into conventional PCI
> slots.
> 

Okay thanks for the correction, so that sounds like for NON_TRANSITIONAL 
we should also be forcing pcieFlags. I've made those changes and updated 
the branch here: https://github.com/crobinso/libvirt/tree/virtio

Thanks,
Cole