[PATCH v2 0/9] memory-backend-file related improvements and VM templating support

[David Hildenbrand <david@redhat.com>]

This is the result of the previous discussion of:
* "[PATCH v2] softmmu/physmem: try opening file readonly before failure
   in file_ram_open" [1]
* "[PATCH v1 0/3] softmmu/physmem: file_ram_open() readonly
   improvements" [2]

After looking into various ways to avoid a new parameter for
memory-backend-file to cleanly support VM templating with R/O files, I
concluded that it might be easier and cleaner to hust have a new parameter.
The alternatives all had their own problems.

Looking back, we could have designed the "readonly=on/off" parameter
slightly differently.

So this series adds a new "rom=on/off/auto" option and wires it up
internally. It uses new internal RAM flags to improve qemu_ram_remap() and
ram_block_discard_range().

Further, improve file_ram_open() with readonly=on and update+add some
documentation.

While working on this and testing some configurations, I realized that
an NVDIMM with label data on ROM does not work as expected (QEMU crashes).
Fix included as patch #1.

No changelog, because too much changed.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Thiner Logoer <logoerthiner1@163.com>
Cc: "Philippe Mathieu-Daudé" <philmd@linaro.org>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Cc: Jagannathan Raman <jag.raman@oracle.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Ani Sinha <anisinha@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Cc: Daniel Henrique Barboza <danielhb413@gmail.com>
Cc: Greg Kurz <groug@kaod.org>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: Eduardo Habkost <eduardo@habkost.net>

[1] https://lkml.kernel.org/r/20230726145912.88545-1-logoerthiner1@163.com
[2] https://lkml.kernel.org/r/20230807190736.572665-1-david@redhat.com

David Hildenbrand (9):
  nvdimm: Reject writing label data to ROM instead of crashing QEMU
  softmmu/physmem: Distinguish between file access mode and mmap
    protection
  backends/hostmem-file: Add "rom" property to support VM templating
    with R/O files
  softmmu/physmem: Remap with proper protection in qemu_ram_remap()
  softmmu/physmem: Bail out early in ram_block_discard_range() with
    readonly files
  softmmu/physmem: Fail creation of new files in file_ram_open() with
    readonly=true
  softmmu/physmem: Never return directories from file_ram_open()
  docs: Don't mention "-mem-path" in multi-process.rst
  docs: Start documenting VM templating

 backends/hostmem-file.c      |  61 +++++++++++++++++++-
 docs/devel/multi-process.rst |   5 +-
 docs/vm-templating.txt       | 109 +++++++++++++++++++++++++++++++++++
 hw/acpi/nvdimm.c             |  11 +++-
 hw/mem/nvdimm.c              |  10 +++-
 hw/ppc/spapr_nvdimm.c        |   3 +-
 include/exec/memory.h        |  14 +++--
 include/exec/ram_addr.h      |   8 +--
 include/hw/mem/nvdimm.h      |   6 ++
 qapi/qom.json                |   6 +-
 qemu-options.hx              |  10 +++-
 softmmu/memory.c             |   8 +--
 softmmu/physmem.c            |  74 +++++++++++++++++-------
 13 files changed, 279 insertions(+), 46 deletions(-)
 create mode 100644 docs/vm-templating.txt

-- 
2.41.0