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

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Message-ID: <ZyOv2E-WEcppbf3G@li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com>
Date: Thu, 31 Oct 2024 17:27:04 +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 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.

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