Re: [RFC] memory.c: improve refcounting for RAM vs MMIO regions

[David Hildenbrand <david@redhat.com>]

On 23.07.25 14:19, Albert Esteve wrote:
> In the last version of the SHMEM MAP/UNMAP [1] there was a
> comment [2] from Stefan about the lifecycle of the memory
> regions.
> 
> After some discussion, David Hildenbrand proposed
> to detect RAM regions and handle refcounting differently
> to clear the initial concern. This RFC patch is
> meant for gathering feedback from others
> (i.e., Paolo Bonzini and Peter Xu).
> 
> [1] https://patchwork.ozlabs.org/project/qemu-devel/list/?series=460121
> [2] https://patchwork.ozlabs.org/comment/3528600/
> 
> ---
> 
> This patch enhances memory_region_ref() and memory_region_unref()
> to handle RAM and MMIO memory regions differently, improving
> reference counting semantics.
> 
> RAM regions now reference/unreference the memory region object
> itself, while MMIO continue to reference/unreference the owner
> device as before.
> 
> An additional qtest has been added to stress the memory
> lifecycle. All tests pass as these changes keep backward
> compatibility (prior behaviour is kept for MMIO regions).
> 
> Signed-off-by: David Hildenbrand <david@redhat.com >
> Signed-off-by: Albert Esteve <aesteve@redhat.com>
> ---
>   system/memory.c            | 22 +++++++++++++----
>   tests/qtest/ivshmem-test.c | 50 ++++++++++++++++++++++++++++++++++++++
>   2 files changed, 67 insertions(+), 5 deletions(-)

Did we discuss extending the doc as well, to clarify which scenario is 
now supported?

-- 
Cheers,

David / dhildenb