Message-ID: <20241025141453.1210600-1-david@redhat.com>
Date: Fri, 25 Oct 2024 16:14:45 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-s390@...r.kernel.org,
	virtualization@...ts.linux.dev,
	linux-doc@...r.kernel.org,
	kvm@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	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: [PATCH v3 0/7] virtio-mem: s390 support

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 Pérez" <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

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