Re: [PATCH 1/9] hw/mem: Add tag support to generic host memory backends

[Alireza Sanaee via qemu development <qemu-devel@nongnu.org>]

On Thu, 26 Mar 2026 11:42:17 +0100
Markus Armbruster <armbru@redhat.com> wrote:

Hi Markus,

> Alireza Sanaee <alireza.sanaee@huawei.com> writes:
> 
> > Add a string tag property to HostMemoryBackend so that backends can be
> > identified by a user-assigned name at runtime. Expose the property through
> > QOM and add a host_memory_backend_find_by_tag() helper that walks the
> > object tree to locate a backend by its tag.  
> 
> Why can't you use the QOM ID?
> 
> $ qemu-system-x86_64 -S -display none -monitor stdio -object memory-backend-ram,id=fred,size=1M
> QEMU 10.2.90 monitor - type 'help' for more information
> (qemu) info qom-tree /objects/fred
> /fred (memory-backend-ram)
>   /fred[0] (memory-region)
> 
>  

Fair question. The ID would have been a solution if it had accepted GUIDs. CXL spec 
requires GUIDs for extents as identification, hence new tag property.

alireza@blue-ocean:~/Downloads$ qemu-system-x86_64 -s -display none -monitor std
io -object memory-backend-ram,id=02bb2436-e87d-4aa1-b2be-aaffdd76bb79,size=1M
qemu-system-x86_64: -object memory-backend-ram,id=02bb2436-e87d-4aa1-b2be-aaffdd
76bb79,size=1M: Parameter 'id' expects an identifier
Identifiers consist of letters, digits, '-', '.', '_', starting with a letter.

Thanks,
Ali