Re: [XENBUS PATCH v3 1/2] Use Windows 10 APIs to inflate/deflate balloon

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 12/06/2025 12:00, Tu Dinh wrote:
> Currently the balloon driver allocates pages as normal memory, which
> causes Windows to report the ballooned memory as kernel-allocated
> instead of unavailable.
>
> Windows 10 provides MM_ALLOCATE_AND_HOT_REMOVE to remove pages from
> the physical memory pool. The removed pages can be added back with
> MmAddPhysicalMemory.
>
> Using this feature, the real VM memory capacity will be correctly
> reported in Task Manager.
>
> Balloon deflation is implemented using calls to MmAddPhysicalMemory on
> contiguous PFN ranges.
>
> Note that MM_ALLOCATE_AND_HOT_REMOVE actually removes the pages from
> memory space, so the resulting MDL will have the MDL_IO_SPACE flag;
> similarly, when probing the freed MDL on deflation, we'll also have to
> set MDL_IO_SPACE.
>
> Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
> ---
> v3: Fix the issue where hot-removed memory will be in I/O space.
> v2: Updated commit message to say what the patch does. No code change.
> ---
>   src/xenbus/balloon.c | 43 ++++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 38 insertions(+), 5 deletions(-)
How much testing has this had? v3 came out of nowhere.