Re: [PATCH 00/10] Introduce virtio-mem <memory/> model

On 1/22/21 6:19 PM, David Hildenbrand wrote: > >> Out of curiosity: are you aware of anyone working in enabling virtio-mem >> for pseries/ppc64? I'm wondering if there's some kind of architecture >> limitation in Power or if it's just a lack of interest. > > I remember there is interest, however: > > - arm64 and x86-64 is used more frequently in applicable (cloud?) setups, so it has high prio > - s390x doesn‘t have any proper memory hot(un)plug, and as I have a strong s399x background, it‘s rather easy for me to implement > - ppc64 at least supports hot(un)plug of DIMMs > > There is nothing fundamental speaking against ppc64 support AFAIR. That's good to hear. > A block size of 16MB should be possible. I‘m planning on looking into it, however, there are a lot of other things on my todo list for virtio-mem. I'm not familiar with the 'block size' concept of the virtio-mem device that would allow for 16MB increments. My knowledge of the pseries kernel/QEMU is that the guest visible memory must always be 256MiB aligned due to PAPR mechanics that forces a memory block to be at least this size. Albeit I believe that there is no constraints of the memory this device is providing being counted as non-hotplugable, then in this case the alignment shouldn't be needed.

But I digress. Thanks for the insights. I'll ping some people inside IBM and see if we have a more immediate use case for virtio-mem in Power. Perhaps we can do some sort of collaboration with your work.