linux-kernel - Re: [PATCH v3 0/7] virtio-mem: s390 support

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Message-ID: <ZyO0lPkLPGnpDKrr@li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com>
Date: Thu, 31 Oct 2024 17:47:16 +0100
From: Sumanth Korikkar <sumanthk@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: 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,
        Heiko Carstens <hca@...ux.ibm.com>, 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>,
        Claudio Imbrenda <imbrenda@...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>,
        Eric Farman <farman@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v3 0/7] virtio-mem: s390 support

On Thu, Oct 31, 2024 at 05:27:06PM +0100, Sumanth Korikkar wrote:
> On Fri, Oct 25, 2024 at 04:14:45PM +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 three 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 properly enter the "kdump mode" in the virtio-mem
> >    driver
> > 
> > kdump support for virtio-mem memory on s390 will be sent out separately.
> > 
> > v2 -> v3
> > * "s390/kdump: make is_kdump_kernel() consistently return "true" in kdump
> >    environments only"
> >  -> Sent out separately [3]
> > * "s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory
> >    devices"
> >  -> No query function for diag500 for now.
> >  -> Update comment above setup_ident_map_size().
> >  -> Optimize/rewrite diag500_storage_limit() [Heiko]
> >  -> Change handling in detect_physmem_online_ranges [Alexander]
> >  -> Improve documentation.
> > * "s390/sparsemem: provide memory_add_physaddr_to_nid() with CONFIG_NUMA"
> >  -> Added after testing on systems with CONFIG_NUMA=y
> > 
> > v1 -> v2:
> > * Document the new diag500 subfunction
> > * Use "s390" instead of "s390x" consistently
> > 
> > [1] https://lkml.kernel.org/r/20241008105455.2302628-1-david@redhat.com
> > [2] https://virtio-mem.gitlab.io/user-guide/user-guide-linux.html
> > [3] https://lkml.kernel.org/r/20241023090651.1115507-1-david@redhat.com
> > 
> > Cc: Heiko Carstens <hca@...ux.ibm.com>
> > Cc: Vasily Gorbik <gor@...ux.ibm.com>
> > Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> > Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
> > Cc: Sven Schnelle <svens@...ux.ibm.com>
> > Cc: Thomas Huth <thuth@...hat.com>
> > Cc: Cornelia Huck <cohuck@...hat.com>
> > Cc: Janosch Frank <frankja@...ux.ibm.com>
> > Cc: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> > Cc: "Michael S. Tsirkin" <mst@...hat.com>
> > Cc: Jason Wang <jasowang@...hat.com>
> > Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > Cc: "Eugenio P?rez" <eperezma@...hat.com>
> > Cc: Eric Farman <farman@...ux.ibm.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Jonathan Corbet <corbet@....net>
> > 
> > David Hildenbrand (7):
> >   Documentation: s390-diag.rst: make diag500 a generic KVM hypercall
> >   Documentation: s390-diag.rst: document diag500(STORAGE LIMIT)
> >     subfunction
> >   s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM
> >     memory devices
> >   virtio-mem: s390 support
> >   lib/Kconfig.debug: default STRICT_DEVMEM to "y" on s390
> >   s390/sparsemem: reduce section size to 128 MiB
> >   s390/sparsemem: provide memory_add_physaddr_to_nid() with CONFIG_NUMA
> > 
> >  Documentation/virt/kvm/s390/s390-diag.rst | 35 +++++++++++++----
> >  arch/s390/boot/physmem_info.c             | 47 ++++++++++++++++++++++-
> >  arch/s390/boot/startup.c                  |  7 +++-
> >  arch/s390/include/asm/physmem_info.h      |  3 ++
> >  arch/s390/include/asm/sparsemem.h         | 10 ++++-
> >  drivers/virtio/Kconfig                    | 12 +++---
> >  lib/Kconfig.debug                         |  2 +-
> >  7 files changed, 98 insertions(+), 18 deletions(-)
> > 
> > 
> > base-commit: ae90f6a6170d7a7a1aa4fddf664fbd093e3023bc
> > -- 
> > 2.46.1
> > 
> 
> Tested successfully various memory hotplug operations on lpar.
> 
Just to be more precise, tested memory hotplug/hotunplug combinations +
Device hotplug/hotunplug operations on guest.

> Tested-by: Sumanth Korikkar <sumanthk@...ux.ibm.com>