linux-kernel - [PATCH v2 1/5] mshv: Only map vp->vp_stats

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Message-Id: <1757546089-2002-2-git-send-email-nunodasneves@linux.microsoft.com>
Date: Wed, 10 Sep 2025 16:14:45 -0700
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	prapal@...ux.microsoft.com,
	easwar.hariharan@...ux.microsoft.com,
	tiala@...rosoft.com,
	anirudh@...rudhrb.com,
	paekkaladevi@...ux.microsoft.com
Cc: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Subject: [PATCH v2 1/5] mshv: Only map vp->vp_stats_pages if on root scheduler

This mapping is only used for checking if the dispatch thread is
blocked. This is only relevant for the root scheduler, so check the
scheduler type to determine whether to map/unmap these pages, instead of
the current check, which is incorrect.

Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Reviewed-by: Anirudh Rayabharam <anirudh@...rudhrb.com>
Reviewed-by: Praveen K Paladugu <prapal@...ux.microsoft.com>
Reviewed-by: Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@...rosoft.com>
---
 drivers/hv/mshv_root_main.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index e3b2bd417c46..24df47726363 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -934,7 +934,11 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
 			goto unmap_register_page;
 	}
 
-	if (hv_parent_partition()) {
+	/*
+	 * This mapping of the stats page is for detecting if dispatch thread
+	 * is blocked - only relevant for root scheduler
+	 */
+	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT) {
 		ret = mshv_vp_stats_map(partition->pt_id, args.vp_index,
 					stats_pages);
 		if (ret)
@@ -963,7 +967,7 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
 	if (mshv_partition_encrypted(partition) && is_ghcb_mapping_available())
 		vp->vp_ghcb_page = page_to_virt(ghcb_page);
 
-	if (hv_parent_partition())
+	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
 		memcpy(vp->vp_stats_pages, stats_pages, sizeof(stats_pages));
 
 	/*
@@ -986,7 +990,7 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
 free_vp:
 	kfree(vp);
 unmap_stats_pages:
-	if (hv_parent_partition())
+	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
 		mshv_vp_stats_unmap(partition->pt_id, args.vp_index);
 unmap_ghcb_page:
 	if (mshv_partition_encrypted(partition) && is_ghcb_mapping_available()) {
@@ -1740,7 +1744,7 @@ static void destroy_partition(struct mshv_partition *partition)
 			if (!vp)
 				continue;
 
-			if (hv_parent_partition())
+			if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
 				mshv_vp_stats_unmap(partition->pt_id, vp->vp_index);
 
 			if (vp->vp_register_page) {
-- 
2.34.1