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

David Hildenbrand
2024-10-25T14:15:09Z

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@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "Eugenio Pérez" <eperezma@redhat.com>
Cc: Eric Farman <farman@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.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