linux-kernel - [PATCH v3 4/6] mshv: Always map child vp stats pages regardless of scheduler type

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Message-ID: <20260114213803.143486-5-nunodasneves@linux.microsoft.com>
Date: Wed, 14 Jan 2026 13:38:01 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mhklinux@...look.com,
	skinsburskii@...ux.microsoft.com
Cc: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	longli@...rosoft.com,
	prapal@...ux.microsoft.com,
	mrathor@...ux.microsoft.com,
	paekkaladevi@...ux.microsoft.com,
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Subject: [PATCH v3 4/6] mshv: Always map child vp stats pages regardless of scheduler type

From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>

Currently vp->vp_stats_pages is only used by the root scheduler for fast
interrupt injection.

Soon, vp_stats_pages will also be needed for exposing child VP stats to
userspace via debugfs. Mapping the pages a second time to a different
address causes an error on L1VH.

Remove the scheduler requirement and always map the vp stats pages.

Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
---
 drivers/hv/mshv_root_main.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index faca3cc63e79..fbfc9e7d9fa4 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -1077,16 +1077,10 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
 			goto unmap_register_page;
 	}
 
-	/*
-	 * 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)
-			goto unmap_ghcb_page;
-	}
+	ret = mshv_vp_stats_map(partition->pt_id, args.vp_index,
+				stats_pages);
+	if (ret)
+		goto unmap_ghcb_page;
 
 	vp = kzalloc(sizeof(*vp), GFP_KERNEL);
 	if (!vp)
@@ -1110,8 +1104,7 @@ 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_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
-		memcpy(vp->vp_stats_pages, stats_pages, sizeof(stats_pages));
+	memcpy(vp->vp_stats_pages, stats_pages, sizeof(stats_pages));
 
 	/*
 	 * Keep anon_inode_getfd last: it installs fd in the file struct and
@@ -1133,8 +1126,7 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
 free_vp:
 	kfree(vp);
 unmap_stats_pages:
-	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
-		mshv_vp_stats_unmap(partition->pt_id, args.vp_index, stats_pages);
+	mshv_vp_stats_unmap(partition->pt_id, args.vp_index, stats_pages);
 unmap_ghcb_page:
 	if (mshv_partition_encrypted(partition) && is_ghcb_mapping_available())
 		hv_unmap_vp_state_page(partition->pt_id, args.vp_index,
@@ -1754,9 +1746,8 @@ static void destroy_partition(struct mshv_partition *partition)
 			if (!vp)
 				continue;
 
-			if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
-				mshv_vp_stats_unmap(partition->pt_id, vp->vp_index,
-						    vp->vp_stats_pages);
+			mshv_vp_stats_unmap(partition->pt_id, vp->vp_index,
+					    vp->vp_stats_pages);
 
 			if (vp->vp_register_page) {
 				(void)hv_unmap_vp_state_page(partition->pt_id,
-- 
2.34.1