Re: [PATCH v2 0/7] virtio-mem: s390 support

Heiko Carstens
2024-10-14T18:57:14Z

On Mon, Oct 14, 2024 at 04:46:12PM +0200, David Hildenbrand wrote:
> Let's finally add s390 support for virtio-mem; my last RFC was sent
> 4 years ago, and a lot changed in the meantime.
>
> The latest QEMU series is available at [1], which contains some more
> details and a usage example on s390 (last patch).
>
> There is not too much in here: The biggest part is querying a new diag(500)
> STORAGE_LIMIT hypercall to obtain the proper "max_physmem_end".
>
> The last two patches are not strictly required but certainly nice-to-have.
>
> Note that -- in contrast to standby memory -- virtio-mem memory must be
> configured to be automatically onlined as soon as hotplugged. The easiest
> approach is using the "memhp_default_state=" kernel parameter or by using
> proper udev rules. More details can be found at [2].
>
> I have reviving+upstreaming a systemd service to handle configuring
> that on my todo list, but for some reason I keep getting distracted ...
>
> I tested various things, including:
> * Various memory hotplug/hotunplug combinations
> * Device hotplug/hotunplug
> * /proc/iomem output
> * reboot
> * kexec
> * kdump: make sure we don't hotplug memory
>
> One remaining work item is kdump support for virtio-mem memory. This will
> be sent out separately once initial support landed.

Besides the open kdump question, which I think is quite important, how
is this supposed to go upstream?

This could go via s390, however in any case this needs reviews and/or
Acks from kvm folks.