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

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Message-ID: <3b5d2bf2-2d27-43a1-86fe-076878823edf@redhat.com>
Date: Thu, 31 Oct 2024 18:30:37 +0100
From: David Hildenbrand <david@...hat.com>
To: Sumanth Korikkar <sumanthk@...ux.ibm.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 31.10.24 17:47, Sumanth Korikkar wrote:
> 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.

Thanks a bunch!

-- 
Cheers,

David / dhildenb