[Qemu-devel] [PATCH v3 0/8] acpi: make ROMs resizeable

["Michael S. Tsirkin" <mst@redhat.com>]

This is v3 of the patchset.
Changes since v2:
    - Address Paolo's comments: drop an unused function, fix up
      comment.

Changes since v1:
    - Any RAM can now be resizeable - there's no requirement
      that it's device RAM any longer.
    - For simplicity, max_size RAM is always pre-allocated
    - Added memory_region_set_size, to keep MR size consistent
      in case MR is guest visible (even though for current users,
      it never is)

At the moment we migrate ROMs which reside in fw cfg, which allows
changing ROM code at will, and supports migrating largish blocks early,
with good performance.
However, we are running into a problem: changing size breaks
migration every time.
This already requires somewhat messy compatibility support in
acpi generation code, and it looks like there'll be more to come.

While recent patches by Paolo and others might make it easier
to keep table size static for specific machine types, having
a safety net in case we do need to change it sounds like
a good idea.

Rather than try to guess the correct size once and for all,
this patchset tries to make code future-proof, by
adding support for resizeable ram blocks.

A (possibly very high) amount of space in ram_addr_t space is reserved
and allocated in host for each block, but never used by fw cfg.
If incoming block size differs from current size, block is
reallocated. FW CFG is also notified and updated accordingly.

As reviewers felt that making all RAM "resizeable" in this
way might make debugging migration harder, these patches
set a per-block flag and only allow resizing for blocks
where this was explicitly requested.

Note: migration stream is unaffected by these patches.
This makes it possible to enable this functionality
unconditionally, for all machine types.

In the future, this API might be handy for other things, besides ROMs.

Michael S. Tsirkin (8):
  memory: add memory_region_set_size
  exec: cpu_physical_memory_set/clear_dirty_range
  exec: split length -> used_length/max_length
  exec: qemu_ram_alloc_resizeable, qemu_ram_resize
  arch_init: support resizing on incoming migration
  memory: API to allocate resizeable RAM MR
  acpi-build: make ROMs RAM blocks resizeable
  qemu_ram_resize: document assumptions

 hw/lm32/lm32_hwsetup.h  |   3 +-
 include/exec/cpu-all.h  |  12 +++--
 include/exec/memory.h   |  34 ++++++++++++
 include/exec/ram_addr.h |  22 ++++++--
 include/hw/loader.h     |   4 +-
 arch_init.c             |  28 +++++-----
 exec.c                  | 136 +++++++++++++++++++++++++++++++++++++-----------
 hw/core/loader.c        |  18 +++++--
 hw/i386/acpi-build.c    |  19 +++++--
 memory.c                |  33 ++++++++++++
 10 files changed, 249 insertions(+), 60 deletions(-)

-- 
MST