Re: [PATCH] mshv: Add an ioctl to scrub partition state

[Mukesh R <mrathor@linux.microsoft.com>]

On 10/28/26 23:27, wei.liu@kernel.org wrote:
> From: John Starks <jostarks@microsoft.com>
> 
> Userspace VMMs need to reset a child partition's hypervisor-managed state
> without destroying its VPs or rebuilding its memory and eventfd
> registrations. Exposing HvCallScrubPartition through generic hypercall
> passthrough would bypass the synchronization and cached-state updates
> needed by the driver.
> 
> Add MSHV_SCRUB_PARTITION as a no-argument partition-fd ioctl. Hold the
> partition mutex and try-lock each populated VP mutex in index order,
> using the partition mutex as the lockdep nesting lock. Return -EBUSY
> without issuing the hypercall if a VP is busy. This excludes VP ioctls
> without waiting indefinitely for a running VP; userspace must stop its
> run threads before requesting scrub.
> 
> After a successful scrub, clear cached intercept suspend so the next run
> clears explicit suspend rather than trying to consume a stale intercept.
> Preserve deferred blocked waits and notification accounting: a VP becoming
> dispatchable does not imply its host notification has already arrived.
> Keep the locks through this update and unwind them on every exit.
> 
> Scrub is nonallocating, so issue one fast hypercall, trace its status and
> return the existing errno translation. Let the hypervisor determine which
> partition configurations support scrub. Device quiescing and restoring
> guest execution state remain userspace responsibilities.
> 
> Signed-off-by: John Starks <jostarks@microsoft.com>
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> 
> ---
> Tested repeated scrub/run, sparse and 64-VP locking, busy unwinding,
> interrupted blocked runs, concurrent memory invalidation and irqfd
> activity on x86-64, and delayed notifications with separate diagnostic
> instrumentation. The affected ARM64 objects compile. ARM64 runtime and
> hypervisor scheduling remain untested. Doorbell delivery across scrub
> works, but exposes an existing eventfd hardirq wait-context warning under
> lockdep, separate from this change.
> 
> GitHub Copilot generated the implementation and test probes, investigated
> locking and notification handling, ran builds and Incubator tests, and
> drafted this description. Human review selected the dedicated ioctl and
> try-lock policy and corrected the nonallocating hypercall contract.
> ---
>   drivers/hv/mshv_root.h         |  1 +
>   drivers/hv/mshv_root_hv_call.c | 11 ++++++++
>   drivers/hv/mshv_root_main.c    | 50 ++++++++++++++++++++++++++++++++++
>   drivers/hv/mshv_trace.h        | 17 ++++++++++++
>   include/hyperv/hvgdk_mini.h    |  1 +
>   include/hyperv/hvhdk.h         |  4 +++
>   include/uapi/linux/mshv.h      | 11 ++++++++
>   7 files changed, 95 insertions(+)
> <snip>


Reviewed-by: Mukesh R <mrathor@linux.microsoft.com>