" split-wx=on|off (enable TCG split w^x mapping)\n"
" tb-size=n (TCG translation block cache size)\n"
" dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n"
+ " eager-split-size=n (KVM Eager Page Split chunk size, default 0, disabled. ARM only)\n"
" notify-vmexit=run|internal-error|disable,notify-window=n (enable notify VM exit and set notify window, x86 only)\n"
" thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL)
SRST
is disabled (dirty-ring-size=0). When enabled, KVM will instead
record dirty pages in a bitmap.
+ ``eager-split-size=n``
+ KVM implements dirty page logging at the PAGE_SIZE granularity and
+ enabling dirty-logging on a huge-page requires breaking it into
+ PAGE_SIZE pages in the first place. KVM on ARM does this splitting
+ lazily by default. There are performance benefits in doing huge-page
+ split eagerly, especially in situations where TLBI costs associated
+ with break-before-make sequences are considerable and also if guest
+ workloads are read intensive. The size here specifies how many pages
+ to break at a time and needs to be a valid block size which is
+ 1GB/2MB/4KB, 32MB/16KB and 512MB/64KB for 4KB/16KB/64KB PAGE_SIZE
+ respectively. Be wary of specifying a higher size as it will have an
+ impact on the memory. By default, this feature is disabled
+ (eager-split-size=0).
+
``notify-vmexit=run|internal-error|disable,notify-window=n``
Enables or disables notify VM exit support on x86 host and specify
the corresponding notify window to trigger the VM exit if enabled.
ERST
DEF("hda", HAS_ARG, QEMU_OPTION_hda,
- "-hda/-hdb file use 'file' as IDE hard disk 0/1 image\n", QEMU_ARCH_ALL)
+ "-hda/-hdb file use 'file' as hard disk 0/1 image\n", QEMU_ARCH_ALL)
DEF("hdb", HAS_ARG, QEMU_OPTION_hdb, "", QEMU_ARCH_ALL)
DEF("hdc", HAS_ARG, QEMU_OPTION_hdc,
- "-hdc/-hdd file use 'file' as IDE hard disk 2/3 image\n", QEMU_ARCH_ALL)
+ "-hdc/-hdd file use 'file' as hard disk 2/3 image\n", QEMU_ARCH_ALL)
DEF("hdd", HAS_ARG, QEMU_OPTION_hdd, "", QEMU_ARCH_ALL)
SRST
``-hda file``
``-hdc file``
\
``-hdd file``
- Use file as hard disk 0, 1, 2 or 3 image (see the :ref:`disk images`
- chapter in the System Emulation Users Guide).
+ Use file as hard disk 0, 1, 2 or 3 image on the default bus of the
+ emulated machine (this is for example the IDE bus on most x86 machines,
+ but it can also be SCSI, virtio or something else on other target
+ architectures). See also the :ref:`disk images` chapter in the System
+ Emulation Users Guide.
ERST
DEF("cdrom", HAS_ARG, QEMU_OPTION_cdrom,
- "-cdrom file use 'file' as IDE cdrom image (cdrom is ide1 master)\n",
+ "-cdrom file use 'file' as CD-ROM image\n",
QEMU_ARCH_ALL)
SRST
``-cdrom file``
- Use file as CD-ROM image (you cannot use ``-hdc`` and ``-cdrom`` at
- the same time). You can use the host CD-ROM by using ``/dev/cdrom``
- as filename.
+ Use file as CD-ROM image on the default bus of the emulated machine
+ (which is IDE1 master on x86, so you cannot use ``-hdc`` and ``-cdrom``
+ at the same time there). On systems that support it, you can use the
+ host CD-ROM by using ``/dev/cdrom`` as filename.
ERST
DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,
they are specified. Note that the 'id' property must be set. These
objects are placed in the '/objects' path.
- ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off``
+ ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto``
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages.
The ``readonly`` option specifies whether the backing file is opened
read-only or read-write (default).
+ The ``rom`` option specifies 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 proper 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`` (default), the value of the
+ ``readonly`` option is used. This option is primarily helpful when
+ we want to have writable RAM in configurations that would
+ traditionally create ROM before the ``rom`` option was introduced:
+ VM templating, where we want to open a file readonly
+ (``readonly=on``) and mark the memory to be private for QEMU
+ (``share=off``). For this use case, we need writable RAM instead
+ of ROM, and want to also set ``rom=off``.
+
``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave``
Creates a memory backend object, which can be used to back the
guest RAM. Memory backend objects offer more control than the