linux-kernel - Re: [PATCH v7 2/7] Drivers: hv: Centralize guest memory region destruction

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Message-ID: <aS14E-QpVccRc6Gz@anirudh-surface.localdomain>
Date: Mon, 1 Dec 2025 11:12:19 +0000
From: Anirudh Rayabharam <anirudh@...rudhrb.com>
To: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/7] Drivers: hv: Centralize guest memory region
 destruction

On Wed, Nov 26, 2025 at 02:08:57AM +0000, Stanislav Kinsburskii wrote:
> Centralize guest memory region destruction to prevent resource leaks and
> inconsistent cleanup across unmap and partition destruction paths.
> 
> Unify region removal, encrypted partition access recovery, and region
> invalidation to improve maintainability and reliability. Reduce code
> duplication and make future updates less error-prone by encapsulating
> cleanup logic in a single helper.
> 
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> Reviewed-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
>  drivers/hv/mshv_root_main.c |   65 ++++++++++++++++++++++---------------------
>  1 file changed, 34 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index fec82619684a..ec18984c3f2d 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -1356,13 +1356,42 @@ mshv_map_user_memory(struct mshv_partition *partition,
>  	return ret;
>  }
>  
> +static void mshv_partition_destroy_region(struct mshv_mem_region *region)
> +{
> +	struct mshv_partition *partition = region->partition;
> +	u32 unmap_flags = 0;
> +	int ret;
> +
> +	hlist_del(&region->hnode);
> +
> +	if (mshv_partition_encrypted(partition)) {
> +		ret = mshv_partition_region_share(region);
> +		if (ret) {
> +			pt_err(partition,
> +			       "Failed to regain access to memory, unpinning user pages will fail and crash the host error: %d\n",
> +			       ret);
> +			return;
> +		}
> +	}
> +
> +	if (region->flags.large_pages)
> +		unmap_flags |= HV_UNMAP_GPA_LARGE_PAGE;
> +
> +	/* ignore unmap failures and continue as process may be exiting */
> +	hv_call_unmap_gpa_pages(partition->pt_id, region->start_gfn,
> +				region->nr_pages, unmap_flags);
> +
> +	mshv_region_invalidate(region);
> +
> +	vfree(region);
> +}
> +
>  /* Called for unmapping both the guest ram and the mmio space */
>  static long
>  mshv_unmap_user_memory(struct mshv_partition *partition,
>  		       struct mshv_user_mem_region mem)
>  {
>  	struct mshv_mem_region *region;
> -	u32 unmap_flags = 0;
>  
>  	if (!(mem.flags & BIT(MSHV_SET_MEM_BIT_UNMAP)))
>  		return -EINVAL;
> @@ -1377,18 +1406,8 @@ mshv_unmap_user_memory(struct mshv_partition *partition,
>  	    region->nr_pages != HVPFN_DOWN(mem.size))
>  		return -EINVAL;
>  
> -	hlist_del(&region->hnode);
> +	mshv_partition_destroy_region(region);
>  
> -	if (region->flags.large_pages)
> -		unmap_flags |= HV_UNMAP_GPA_LARGE_PAGE;
> -
> -	/* ignore unmap failures and continue as process may be exiting */
> -	hv_call_unmap_gpa_pages(partition->pt_id, region->start_gfn,
> -				region->nr_pages, unmap_flags);
> -
> -	mshv_region_invalidate(region);
> -
> -	vfree(region);
>  	return 0;
>  }
>  
> @@ -1724,8 +1743,8 @@ static void destroy_partition(struct mshv_partition *partition)
>  {
>  	struct mshv_vp *vp;
>  	struct mshv_mem_region *region;
> -	int i, ret;
>  	struct hlist_node *n;
> +	int i;
>  
>  	if (refcount_read(&partition->pt_ref_count)) {
>  		pt_err(partition,
> @@ -1789,25 +1808,9 @@ static void destroy_partition(struct mshv_partition *partition)
>  
>  	remove_partition(partition);
>  
> -	/* Remove regions, regain access to the memory and unpin the pages */
>  	hlist_for_each_entry_safe(region, n, &partition->pt_mem_regions,
> -				  hnode) {
> -		hlist_del(&region->hnode);
> -
> -		if (mshv_partition_encrypted(partition)) {
> -			ret = mshv_partition_region_share(region);
> -			if (ret) {
> -				pt_err(partition,
> -				       "Failed to regain access to memory, unpinning user pages will fail and crash the host error: %d\n",
> -				      ret);
> -				return;
> -			}
> -		}
> -
> -		mshv_region_invalidate(region);
> -
> -		vfree(region);
> -	}
> +				  hnode)
> +		mshv_partition_destroy_region(region);
>  
>  	/* Withdraw and free all pages we deposited */
>  	hv_call_withdraw_memory(U64_MAX, NUMA_NO_NODE, partition->pt_id);
> 
> 

Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>