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@xxxxxxxxxx [2] https://virtio-mem.gitlab.io/user-guide/user-guide-linux.html [3] https://lkml.kernel.org/r/20241023090651.1115507-1-david@xxxxxxxxxx Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> Cc: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: Thomas Huth <thuth@xxxxxxxxxx> Cc: Cornelia Huck <cohuck@xxxxxxxxxx> Cc: Janosch Frank <frankja@xxxxxxxxxxxxx> Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Jason Wang <jasowang@xxxxxxxxxx> Cc: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> Cc: "Eugenio Pérez" <eperezma@xxxxxxxxxx> Cc: Eric Farman <farman@xxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> 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
