[PATCH RFCv2 0/6] s390x: initial support for virtio-mem

[David Hildenbrand <david@redhat.com>]

This wires up the initial, basic version of virito-mem for s390x. General
information about virtio-mem can be found at [1] and in QEMU commit [2].
Patch #5 contains a short example for s390x.

virtio-mem for x86-64 Linux is part of v5.8-rc1. A branch with a s390x
prototype can be found at:
    git@github.com:davidhildenbrand/linux.git virtio-mem-s390x

Note that the kernel should either be compiled via
 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE, or "memhp_default_state=online"
 should be passed on the kernel cmdline.

This series can be found at:
    git@github.com:davidhildenbrand/qemu.git virtio-mem-s390x-rfcv2

Related to s390x, we'll have to tackle migration of storage keys and
storage attributes (especially, skipping unplugged parts). Not sure if
I am missing something else (any ideas?). For virtio-mem in general, there
are a couple of TODOs, e.g., documented in [1] and [2], both in QEMU and
Linux. However, the basics are around.

I only tested this with fairly small amount of RAM in a z/VM environemnt
and under TCG ...

[1] https://virtio-mem.gitlab.io/
[2] 910b25766b33 ("virtio-mem: Paravirtualized memory hot(un)plug")

RFCv1 -> RFCv2:
- "s390x/diag: no need to check for PGM_PRIVILEGED in diag308"
-- Added
- "s390x/diag: implement diag260"
-- Implement according to doc (fix error cases)
-- Implement subcode 0xc.
-- Enable the new diag unconditionally
- "s390x: prepare device memory address space"
-- Expose maxram size now via diag260 (0xc), not via SCLP. Unfmodified
   guests can now boot without any issues. This needed kernel changes
   (updated the Linux kernel branch)
- "s390x: implement virtio-mem-ccw"
-- Force virtio revision 1

David Hildenbrand (6):
  s390x: move setting of maximum ram size to machine init
  s390x/diag: no need to check for PGM_PRIVILEGED in diag308
  s390x/diag: implement diag260
  s390x: prepare device memory address space
  s390x: implement virtio-mem-ccw
  s390x: initial support for virtio-mem

 hw/s390x/Kconfig                   |   1 +
 hw/s390x/Makefile.objs             |   1 +
 hw/s390x/s390-virtio-ccw.c         | 178 ++++++++++++++++++++++++++++-
 hw/s390x/sclp.c                    |  23 +---
 hw/s390x/virtio-ccw-mem.c          | 167 +++++++++++++++++++++++++++
 hw/s390x/virtio-ccw.h              |  13 +++
 hw/virtio/virtio-mem.c             |   2 +
 include/hw/s390x/s390-virtio-ccw.h |   3 +
 target/s390x/diag.c                |  62 +++++++++-
 target/s390x/internal.h            |   2 +
 target/s390x/kvm.c                 |  11 ++
 target/s390x/misc_helper.c         |   6 +
 target/s390x/translate.c           |   7 ++
 13 files changed, 446 insertions(+), 30 deletions(-)
 create mode 100644 hw/s390x/virtio-ccw-mem.c

-- 
2.26.2