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

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Message-ID: <20241015095735.189a93a9@p-imbrenda.boeblingen.de.ibm.com>
Date: Tue, 15 Oct 2024 09:57:35 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: Heiko Carstens <hca@...ux.ibm.com>
Cc: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        virtualization@...ts.linux.dev, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Christian Borntraeger
 <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Thomas
 Huth <thuth@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Janosch Frank
 <frankja@...ux.ibm.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang
 <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio
 Pérez <eperezma@...hat.com>,
        Andrew Morton
 <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v2 0/7] virtio-mem: s390 support

On Mon, 14 Oct 2024 20:56:59 +0200
Heiko Carstens <hca@...ux.ibm.com> wrote:

> 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.

we're working on it :)