Merge tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support and document VM templating with R/O files using a new "rom"
  parameter for memory-backend-file
- Some cleanups and fixes around NVDIMMs and R/O file handling for guest
  RAM
- Optimize ioeventfd updates by skipping address spaces that are not
  applicable

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# gpg: Signature made Tue 19 Sep 2023 06:25:45 EDT
# gpg:                using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
# gpg:                issuer "david@redhat.com"
# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg:                 aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg:                 aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D  FCCA 4DDE 10F7 00FF 835A

* tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu:
  memory: avoid updating ioeventfds for some address_space
  machine: Improve error message when using default RAM backend id
  softmmu/physmem: Hint that "readonly=on,rom=off" exists when opening file R/W for private mapping fails
  docs: Start documenting VM templating
  docs: Don't mention "-mem-path" in multi-process.rst
  softmmu/physmem: Never return directories from file_ram_open()
  softmmu/physmem: Fail creation of new files in file_ram_open() with readonly=true
  softmmu/physmem: Bail out early in ram_block_discard_range() with readonly files
  softmmu/physmem: Remap with proper protection in qemu_ram_remap()
  backends/hostmem-file: Add "rom" property to support VM templating with R/O files
  softmmu/physmem: Distinguish between file access mode and mmap protection
  nvdimm: Reject writing label data to ROM instead of crashing QEMU

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/qapi/qom.json b/qapi/qom.json
index fa3e88c..c53ef97 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -668,6 +668,20 @@
 # @readonly: if true, the backing file is opened read-only; if false,
 #     it is opened read-write.  (default: false)
 #
+# @rom: whether to create Read Only Memory (ROM) that cannot be modified
+#       by the VM.  Any write attempts to such ROM will be denied.  Most
+#       use cases want writable RAM instead of ROM.  However, selected use
+#       cases, like R/O NVDIMMs, can benefit from ROM.  If set to 'on',
+#       create ROM; if set to 'off', create writable RAM;  if set to
+#       'auto', the value of the @readonly property is used.  This
+#       property is primarily helpful when we want to have proper RAM in
+#       configurations that would traditionally create ROM before this
+#       property was introduced: VM templating, where we want to open a
+#       file readonly (@readonly set to true) and mark the memory to be
+#       private for QEMU (@share set to false).  For this use case, we need
+#       writable RAM instead of ROM, and want to set this property to 'off'.
+#       (default: auto, since 8.2)
+#
 # Since: 2.1
 ##
 { 'struct': 'MemoryBackendFileProperties',
@@ -677,7 +691,8 @@
             '*discard-data': 'bool',
             'mem-path': 'str',
             '*pmem': { 'type': 'bool', 'if': 'CONFIG_LIBPMEM' },
-            '*readonly': 'bool' } }
+            '*readonly': 'bool',
+            '*rom': 'OnOffAuto' } }
 
 ##
 # @MemoryBackendMemfdProperties: