mshv: Centralize guest memory region destruction

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@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

Author: Stanislav Kinsburskii

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);