Message-Id: <20260204174237.1201153-2-anirudh@anirudhrb.com>
Date: Wed,  4 Feb 2026 17:42:36 +0000
From: Anirudh Rayabharam <anirudh@...rudhrb.com>
To: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	longli@...rosoft.com,
	linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: anirudh@...rudhrb.com
Subject: [PATCH v3 1/2] mshv: refactor synic init and cleanup

From: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>

Rename mshv_synic_init() to mshv_synic_cpu_init() and
mshv_synic_cleanup() to mshv_synic_cpu_exit() to better reflect that
these functions handle per-cpu synic setup and teardown.

Use mshv_synic_init/cleanup() to perform init/cleanup that is not per-cpu.
Move all the synic related setup from mshv_parent_partition_init.

Move the reboot notifier to mshv_synic.c because it currently only
operates on the synic cpuhp state.

Move out synic_pages from the global mshv_root since it's use is now
completely local to mshv_synic.c.

This is in preparation for the next patch which will add more stuff to
mshv_synic_init().

No functional change.

Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>
---
 drivers/hv/mshv_root.h      |  5 ++-
 drivers/hv/mshv_root_main.c | 59 +++++-------------------------
 drivers/hv/mshv_synic.c     | 71 +++++++++++++++++++++++++++++++++----
 3 files changed, 75 insertions(+), 60 deletions(-)

diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
index 3c1d88b36741..26e0320c8097 100644
--- a/drivers/hv/mshv_root.h
+++ b/drivers/hv/mshv_root.h
@@ -183,7 +183,6 @@ struct hv_synic_pages {
 };
 
 struct mshv_root {
-	struct hv_synic_pages __percpu *synic_pages;
 	spinlock_t pt_ht_lock;
 	DECLARE_HASHTABLE(pt_htable, MSHV_PARTITIONS_HASH_BITS);
 	struct hv_partition_property_vmm_capabilities vmm_caps;
@@ -242,8 +241,8 @@ int mshv_register_doorbell(u64 partition_id, doorbell_cb_t doorbell_cb,
 void mshv_unregister_doorbell(u64 partition_id, int doorbell_portid);
 
 void mshv_isr(void);
-int mshv_synic_init(unsigned int cpu);
-int mshv_synic_cleanup(unsigned int cpu);
+int mshv_synic_init(struct device *dev);
+void mshv_synic_cleanup(void);
 
 static inline bool mshv_partition_encrypted(struct mshv_partition *partition)
 {
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 681b58154d5e..7c1666456e78 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -2035,7 +2035,6 @@ mshv_dev_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
-static int mshv_cpuhp_online;
 static int mshv_root_sched_online;
 
 static const char *scheduler_type_to_string(enum hv_scheduler_type type)
@@ -2198,40 +2197,14 @@ root_scheduler_deinit(void)
 	free_percpu(root_scheduler_output);
 }
 
-static int mshv_reboot_notify(struct notifier_block *nb,
-			      unsigned long code, void *unused)
-{
-	cpuhp_remove_state(mshv_cpuhp_online);
-	return 0;
-}
-
-struct notifier_block mshv_reboot_nb = {
-	.notifier_call = mshv_reboot_notify,
-};
-
 static void mshv_root_partition_exit(void)
 {
-	unregister_reboot_notifier(&mshv_reboot_nb);
 	root_scheduler_deinit();
 }
 
 static int __init mshv_root_partition_init(struct device *dev)
 {
-	int err;
-
-	err = root_scheduler_init(dev);
-	if (err)
-		return err;
-
-	err = register_reboot_notifier(&mshv_reboot_nb);
-	if (err)
-		goto root_sched_deinit;
-
-	return 0;
-
-root_sched_deinit:
-	root_scheduler_deinit();
-	return err;
+	return root_scheduler_init(dev);
 }
 
 static void mshv_init_vmm_caps(struct device *dev)
@@ -2276,31 +2249,18 @@ static int __init mshv_parent_partition_init(void)
 			MSHV_HV_MAX_VERSION);
 	}
 
-	mshv_root.synic_pages = alloc_percpu(struct hv_synic_pages);
-	if (!mshv_root.synic_pages) {
-		dev_err(dev, "Failed to allocate percpu synic page\n");
-		ret = -ENOMEM;
+	ret = mshv_synic_init(dev);
+	if (ret)
 		goto device_deregister;
-	}
-
-	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mshv_synic",
-				mshv_synic_init,
-				mshv_synic_cleanup);
-	if (ret < 0) {
-		dev_err(dev, "Failed to setup cpu hotplug state: %i\n", ret);
-		goto free_synic_pages;
-	}
-
-	mshv_cpuhp_online = ret;
 
 	ret = mshv_retrieve_scheduler_type(dev);
 	if (ret)
-		goto remove_cpu_state;
+		goto synic_cleanup;
 
 	if (hv_root_partition())
 		ret = mshv_root_partition_init(dev);
 	if (ret)
-		goto remove_cpu_state;
+		goto synic_cleanup;
 
 	mshv_init_vmm_caps(dev);
 
@@ -2318,10 +2278,8 @@ static int __init mshv_parent_partition_init(void)
 exit_partition:
 	if (hv_root_partition())
 		mshv_root_partition_exit();
-remove_cpu_state:
-	cpuhp_remove_state(mshv_cpuhp_online);
-free_synic_pages:
-	free_percpu(mshv_root.synic_pages);
+synic_cleanup:
+	mshv_synic_cleanup();
 device_deregister:
 	misc_deregister(&mshv_dev);
 	return ret;
@@ -2335,8 +2293,7 @@ static void __exit mshv_parent_partition_exit(void)
 	mshv_irqfd_wq_cleanup();
 	if (hv_root_partition())
 		mshv_root_partition_exit();
-	cpuhp_remove_state(mshv_cpuhp_online);
-	free_percpu(mshv_root.synic_pages);
+	mshv_synic_cleanup();
 }
 
 module_init(mshv_parent_partition_init);
diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
index f8b0337cdc82..074e37c48876 100644
--- a/drivers/hv/mshv_synic.c
+++ b/drivers/hv/mshv_synic.c
@@ -12,11 +12,16 @@
 #include <linux/mm.h>
 #include <linux/io.h>
 #include <linux/random.h>
+#include <linux/cpuhotplug.h>
+#include <linux/reboot.h>
 #include <asm/mshyperv.h>
 
 #include "mshv_eventfd.h"
 #include "mshv.h"
 
+static int synic_cpuhp_online;
+static struct hv_synic_pages __percpu *synic_pages;
+
 static u32 synic_event_ring_get_queued_port(u32 sint_index)
 {
 	struct hv_synic_event_ring_page **event_ring_page;
@@ -26,7 +31,7 @@ static u32 synic_event_ring_get_queued_port(u32 sint_index)
 	u32 message;
 	u8 tail;
 
-	spages = this_cpu_ptr(mshv_root.synic_pages);
+	spages = this_cpu_ptr(synic_pages);
 	event_ring_page = &spages->synic_event_ring_page;
 	synic_eventring_tail = (u8 **)this_cpu_ptr(hv_synic_eventring_tail);
 
@@ -393,7 +398,7 @@ mshv_intercept_isr(struct hv_message *msg)
 
 void mshv_isr(void)
 {
-	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
+	struct hv_synic_pages *spages = this_cpu_ptr(synic_pages);
 	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_message *msg;
 	bool handled;
@@ -446,7 +451,7 @@ void mshv_isr(void)
 	}
 }
 
-int mshv_synic_init(unsigned int cpu)
+static int mshv_synic_cpu_init(unsigned int cpu)
 {
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
@@ -455,7 +460,7 @@ int mshv_synic_init(unsigned int cpu)
 	union hv_synic_sint sint;
 #endif
 	union hv_synic_scontrol sctrl;
-	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
+	struct hv_synic_pages *spages = this_cpu_ptr(synic_pages);
 	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_synic_event_flags_page **event_flags_page =
 			&spages->synic_event_flags_page;
@@ -542,14 +547,14 @@ int mshv_synic_init(unsigned int cpu)
 	return -EFAULT;
 }
 
-int mshv_synic_cleanup(unsigned int cpu)
+static int mshv_synic_cpu_exit(unsigned int cpu)
 {
 	union hv_synic_sint sint;
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
 	union hv_synic_sirbp sirbp;
 	union hv_synic_scontrol sctrl;
-	struct hv_synic_pages *spages = this_cpu_ptr(mshv_root.synic_pages);
+	struct hv_synic_pages *spages = this_cpu_ptr(synic_pages);
 	struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
 	struct hv_synic_event_flags_page **event_flags_page =
 		&spages->synic_event_flags_page;
@@ -663,3 +668,57 @@ mshv_unregister_doorbell(u64 partition_id, int doorbell_portid)
 
 	mshv_portid_free(doorbell_portid);
 }
+
+static int mshv_synic_reboot_notify(struct notifier_block *nb,
+			      unsigned long code, void *unused)
+{
+	if (!hv_root_partition())
+		return 0;
+
+	cpuhp_remove_state(synic_cpuhp_online);
+	return 0;
+}
+
+static struct notifier_block mshv_synic_reboot_nb = {
+	.notifier_call = mshv_synic_reboot_notify,
+};
+
+int __init mshv_synic_init(struct device *dev)
+{
+	int ret = 0;
+
+	synic_pages = alloc_percpu(struct hv_synic_pages);
+	if (!synic_pages) {
+		dev_err(dev, "Failed to allocate percpu synic page\n");
+		return -ENOMEM;
+	}
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mshv_synic",
+				mshv_synic_cpu_init,
+				mshv_synic_cpu_exit);
+	if (ret < 0) {
+		dev_err(dev, "Failed to setup cpu hotplug state: %i\n", ret);
+		goto free_synic_pages;
+	}
+
+	synic_cpuhp_online = ret;
+
+	ret = register_reboot_notifier(&mshv_synic_reboot_nb);
+	if (ret)
+		goto remove_cpuhp_state;
+
+	return 0;
+
+remove_cpuhp_state:
+	cpuhp_remove_state(synic_cpuhp_online);
+free_synic_pages:
+	free_percpu(synic_pages);
+	return ret;
+}
+
+void mshv_synic_cleanup(void)
+{
+	unregister_reboot_notifier(&mshv_synic_reboot_nb);
+	cpuhp_remove_state(synic_cpuhp_online);
+	free_percpu(synic_pages);
+}
-- 
2.34.1

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