[PATCH 14/17] mshv: Notifier framework for EOI for level triggered interrupts

[Vineeth Pillai]

A simple in-kernel notifier framework for EOI. Callbacks can be
registered for EOI for level-triggered interrupts. This is to be
used for irqfd support for level-triggered interrupts.

Signed-off-by: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx>
---
 drivers/hv/hv_eventfd.c      | 38 ++++++++++++++++++++++++++++++++++++
 drivers/hv/hv_synic.c        | 22 +++++++++++++++++++++
 drivers/hv/mshv_main.c       |  4 ++++
 include/linux/mshv.h         |  9 +++++++++
 include/linux/mshv_eventfd.h |  6 ++++++
 5 files changed, 79 insertions(+)

diff --git a/drivers/hv/hv_eventfd.c b/drivers/hv/hv_eventfd.c
index 5ed77901fb0b..0bfb088dcb80 100644
--- a/drivers/hv/hv_eventfd.c
+++ b/drivers/hv/hv_eventfd.c
@@ -22,6 +22,44 @@
 
 static struct workqueue_struct *irqfd_cleanup_wq;
 
+void
+mshv_register_irq_ack_notifier(struct mshv_partition *partition,
+			       struct mshv_irq_ack_notifier *mian)
+{
+	spin_lock(&partition->irq_lock);
+	hlist_add_head_rcu(&mian->link, &partition->irq_ack_notifier_list);
+	spin_unlock(&partition->irq_lock);
+}
+
+void
+mshv_unregister_irq_ack_notifier(struct mshv_partition *partition,
+				 struct mshv_irq_ack_notifier *mian)
+{
+	spin_lock(&partition->irq_lock);
+	hlist_del_init_rcu(&mian->link);
+	spin_unlock(&partition->irq_lock);
+	synchronize_rcu();
+}
+
+bool
+mshv_notify_acked_gsi(struct mshv_partition *partition, int gsi)
+{
+	struct mshv_irq_ack_notifier *mian;
+	bool acked = false;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(mian, &partition->irq_ack_notifier_list,
+			link) {
+		if (mian->gsi == gsi) {
+			mian->irq_acked(mian);
+			acked = true;
+		}
+	}
+	rcu_read_unlock();
+
+	return acked;
+}
+
 static void
 irqfd_inject(struct mshv_kernel_irqfd *irqfd)
 {
diff --git a/drivers/hv/hv_synic.c b/drivers/hv/hv_synic.c
index af6653967209..1296928675e3 100644
--- a/drivers/hv/hv_synic.c
+++ b/drivers/hv/hv_synic.c
@@ -14,6 +14,7 @@
 #include <linux/io.h>
 #include <linux/random.h>
 #include <linux/mshv.h>
+#include <linux/mshv_eventfd.h>
 #include <asm/mshyperv.h>
 
 #include "mshv.h"
@@ -158,6 +159,27 @@ mshv_intercept_isr(struct hv_message *msg)
 		goto unlock_out;
 	}
 
+	if (msg->header.message_type == HVMSG_X64_APIC_EOI) {
+		/*
+		 * Check if this gsi is registered in the
+		 * ack_notifier list and invoke the callback
+		 * if registered.
+		 */
+		struct hv_x64_apic_eoi_message *eoi_msg =
+			(struct hv_x64_apic_eoi_message *)msg->u.payload;
+
+		/*
+		 * If there is a notifier, the ack callback is supposed
+		 * to handle the VMEXIT. So we need not pass this message
+		 * to vcpu thread.
+		 */
+		if (mshv_notify_acked_gsi(partition,
+					eoi_msg->interrupt_vector)) {
+			handled = true;
+			goto unlock_out;
+		}
+	}
+
 	/*
 	 * Since we directly index the vp, and it has to exist for us to be here
 	 * (because the vp is only deleted when the partition is), no additional
diff --git a/drivers/hv/mshv_main.c b/drivers/hv/mshv_main.c
index e1caecd27f09..6f93813ad465 100644
--- a/drivers/hv/mshv_main.c
+++ b/drivers/hv/mshv_main.c
@@ -1047,6 +1047,10 @@ mshv_ioctl_create_partition(void __user *user_arg)
 
 	mutex_init(&partition->mutex);
 
+	spin_lock_init(&partition->irq_lock);
+
+	INIT_HLIST_HEAD(&partition->irq_ack_notifier_list);
+
 	fd = get_unused_fd_flags(O_CLOEXEC);
 	if (fd < 0) {
 		ret = fd;
diff --git a/include/linux/mshv.h b/include/linux/mshv.h
index 217c91725828..2cee4832fc7f 100644
--- a/include/linux/mshv.h
+++ b/include/linux/mshv.h
@@ -35,6 +35,12 @@ struct mshv_mem_region {
 	struct page **pages;
 };
 
+struct mshv_irq_ack_notifier {
+	struct hlist_node link;
+	unsigned int gsi;
+	void (*irq_acked)(struct mshv_irq_ack_notifier *mian);
+};
+
 struct mshv_partition {
 	u64 id;
 	refcount_t ref_count;
@@ -48,6 +54,9 @@ struct mshv_partition {
 		struct mshv_vp *array[MSHV_MAX_VPS];
 	} vps;
 
+	spinlock_t irq_lock;
+	struct hlist_head irq_ack_notifier_list;
+
 	struct {
 		spinlock_t        lock;
 		struct list_head  items;
diff --git a/include/linux/mshv_eventfd.h b/include/linux/mshv_eventfd.h
index fd0012f72616..b4d587208294 100644
--- a/include/linux/mshv_eventfd.h
+++ b/include/linux/mshv_eventfd.h
@@ -15,6 +15,12 @@
 void mshv_eventfd_init(struct mshv_partition *partition);
 void mshv_eventfd_release(struct mshv_partition *partition);
 
+void mshv_register_irq_ack_notifier(struct mshv_partition *partition,
+				    struct mshv_irq_ack_notifier *mian);
+void mshv_unregister_irq_ack_notifier(struct mshv_partition *partition,
+			struct mshv_irq_ack_notifier *mian);
+bool mshv_notify_acked_gsi(struct mshv_partition *partition, int gsi);
+
 struct mshv_kernel_irqfd {
 	struct mshv_partition     *partition;
 	struct eventfd_ctx        *eventfd;
-- 
2.25.1