Re: [PATCH v4 10/14] memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()

[Peter Xu]

On Fri, Mar 19, 2021 at 11:12:26AM +0100, David Hildenbrand wrote:
> Let's introduce RAM_NORESERVE, allowing mmap'ing with MAP_NORESERVE. The
> new flag has the following semantics:
> 
> "
> RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or huge
> pages if applicable) is skipped: will bail out if not supported. When not
> set, the OS might do the reservation, depending on OS support.
> "
> 
> Allow passing it into:
> - memory_region_init_ram_nomigrate()
> - memory_region_init_resizeable_ram()
> - memory_region_init_ram_from_file()
> 
> ... and teach qemu_ram_mmap() and qemu_anon_ram_alloc() about the flag.
> Bail out if the flag is not supported, which is the case right now for
> both, POSIX and win32. We will add Linux support next and allow specifying
> RAM_NORESERVE via memory backends.
> 
> The target use case is virtio-mem, which dynamically exposes memory
> inside a large, sparse memory area to the VM.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu