On Thu, 14 Jan 2021 20:38:01 +0100
Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 11/01/21 23:27, Igor Mammedov wrote:
> > Add documentation for '-machine memory-backend' CLI option and
> > how to use it.
> >
> > PS:
> > While at it add a comment to x-use-canonical-path-for-ramblock-id,
> > to make sure it won't go away by accident.
> >
> > Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> > ---
> > backends/hostmem.c | 8 ++++++++
> > qemu-options.hx | 25 ++++++++++++++++++++++++-
> > 2 files changed, 32 insertions(+), 1 deletion(-)
> >
> > diff --git a/backends/hostmem.c b/backends/hostmem.c
> > index 4bde00e8e7..f6f4e818c7 100644
> > --- a/backends/hostmem.c
> > +++ b/backends/hostmem.c
> > @@ -497,6 +497,14 @@ host_memory_backend_class_init(ObjectClass *oc, void
> > *data)
> > host_memory_backend_get_share, host_memory_backend_set_share);
> > object_class_property_set_description(oc, "share",
> > "Mark the memory as private to QEMU or shared");
> > + /*
> > + * Do not delete/rename option till 4.0 and older machine types exist,
> > + * Option will be used by upper layers to override (disable) canonical
> > path
> > + * for ramblock-id set by compat properties on old machine types ( <=
> > 4.0),
> > + * to keep migration working when backend is used for main RAM with
> > + * -machine memory-backend= option (main RAM historically used
> > prefix-less
> > + * ramblock-id).
> > + */
> > object_class_property_add_bool(oc,
> > "x-use-canonical-path-for-ramblock-id",
> > host_memory_backend_get_use_canonical_path,
> > host_memory_backend_set_use_canonical_path);
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 459c916d3d..c02628bd26 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -35,7 +35,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
> > " suppress-vmdesc=on|off disables self-describing
> > migration (default=off)\n"
> > " nvdimm=on|off controls NVDIMM support
> > (default=off)\n"
> > " memory-encryption=@var{} memory encryption object to
> > use (default=none)\n"
> > - " hmat=on|off controls ACPI HMAT support
> > (default=off)\n",
> > + " hmat=on|off controls ACPI HMAT support
> > (default=off)\n"
> > + " memory-backend='backend-id' specifies explicitly
> > provided backend for main RAM (default=none)\n",
> > QEMU_ARCH_ALL)
> > SRST
> > ``-machine [type=]name[,prop=value[,...]]``
> > @@ -96,6 +97,28 @@ SRST
> > ``hmat=on|off``
> > Enables or disables ACPI Heterogeneous Memory Attribute Table
> > (HMAT) support. The default is off.
> > +
> > + ``memory-backend='id'``
> > + An alternative to legacy ``-mem-path`` and ``mem-prealloc``
> > options.
> > + Allows to use a memory backend as main RAM.
> > +
> > + For example:
> > + ::
> > + -object
> > memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on
> > + -machine memory-backend=pc.ram
> > + -m 512M
> > +
> > + Migration compatibility note:
> > + a) as backend id one shall use value of 'default-ram-id',
> > advertised by
> > + machine type (available via ``query-machines`` QMP command)
> > + b) for machine types 4.0 and older, user shall
> > + use ``x-use-canonical-path-for-ramblock-id=on`` backend option,
1) should be
s/on=off/
> > + if migration to/from old QEMU (<5.0) is expected.
> > + For example:
> > + ::
> > + -object
> > memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=on
> > + -machine memory-backend=pc.ram
> > + -m 512M
> > ERST
> >
> > HXCOMM Deprecated by -machine
> >
>
> Queued, thanks.
Paolo,
can you drop this patch fro your queue, pls?
it has a mistake (1)
v3 is in process of cooking, once there is some agreement I'll post it.
>
> Paolo
>
>
