Re: [PATCH v2 6/6] mshv: unmap debugfs stats pages on kexec

[Anirudh Rayabharam]

On Fri, Apr 03, 2026 at 12:06:12PM -0700, Jork Loeser wrote:
> On L1VH, debugfs stats pages are overlay pages: the kernel allocates
> them and registers the GPAs with the hypervisor via
> HVCALL_MAP_STATS_PAGE2. These overlay mappings persist in the
> hypervisor across kexec. If the kexec'd kernel reuses those physical
> pages, the hypervisor's overlay semantics cause a machine check
> exception.
> 
> Fix this by calling mshv_debugfs_exit() from the reboot notifier,
> which issues HVCALL_UNMAP_STATS_PAGE for each mapped stats page before
> kexec. This releases the overlay bindings so the physical pages can be
> safely reused. Guard mshv_debugfs_exit() against being called when
> init failed.
> 
> Signed-off-by: Jork Loeser <jloeser@xxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/hv/mshv_debugfs.c   | 7 ++++++-
>  drivers/hv/mshv_root_main.c | 1 +
>  2 files changed, 7 insertions(+), 1 deletion(-)

Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@xxxxxxxxxxxxx>