Re: [PATCH v1] vhost-vdpa: Set discarding of RAM broken when initializing the backend

[David Hildenbrand <david@redhat.com>]

On 04.03.21 10:32, Jason Wang wrote:
> 
> On 2021/3/3 6:26 下午, David Hildenbrand wrote:
>> On 03.03.21 03:53, Jason Wang wrote:
>>>
>>> On 2021/3/3 12:21 上午, David Hildenbrand wrote:
>>>> Similar to VFIO, vDPA will go ahead an map+pin all guest memory. Memory
>>>> that used to be discarded will get re-populated and if we
>>>> discard+re-access memory after mapping+pinning, the pages mapped
>>>> into the
>>>> vDPA IOMMU will go out of sync with the actual pages mapped into the
>>>> user
>>>> space page tables.
>>>>
>>>> Set discarding of RAM broken such that:
>>>> - virtio-mem and vhost-vdpa run mutually exclusive
>>>> - virtio-balloon is inhibited and no memory discards will get issued
>>>>
>>>> In the future, we might be able to support coordinated discarding of
>>>> RAM
>>>> as used by virtio-mem and as planned for VFIO.
>>>>
>>>> Cc: Jason Wang <jasowang@redhat.com>
>>>> Cc: Michael S. Tsirkin <mst@redhat.com>
>>>> Cc: Cindy Lu <lulu@redhat.com>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>
>>>
>>> Acked-by: Jason Wang <jasowang@redhat.com>
>>>
>>>
>>>> ---
>>>>
>>>> Note: I was not actually able to reproduce/test as I fail to get the
>>>> vdpa_sim/vdpa_sim_net running on upstream Linux (whetever vdpa,
>>>> vhost_vdpa,
>>>> vdpa_sim, vdpa_sim_net modules I probe, and in which order, no vdpa
>>>> devices
>>>> appear under /sys/bus/vdpa/devices/ or /dev/).
>>>
>>>
>>> The device creation was switched to use vdpa tool that is integrated
>>> with iproue2[1].
>>>
>>> [1]
>>> https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/commit/?id=143610383da51e1f868c6d5a2a5e2fb552293d18
>>>
>>
>> It would be great to document that somewhere if not already done. I
>> only found older RH documentations that were not aware of that. I'll
>> give it a try - thanks!
> 
> 
> Will think about this. Which RH doc do you refer here? Is this the
> redhat blog?

https://www.redhat.com/en/blog/hands-vdpa-what-do-you-do-when-you-aint-got-hardware

As it's supposed to be from October 14, 2020 I was surprised to not get 
it running (even with older kernels IIRC).

-- 
Thanks,

David / dhildenb