powerpc/pseries: Enable HVPIPE event message interrupt

JIRA: https://issues.redhat.com/browse/RHEL-101849

Conflicts:
	- Use rtas_token() instead of rtas_function_token()

commit b48b6cc
Author: Haren Myneni <haren@linux.ibm.com>
Date:   Tue Sep 9 01:43:59 2025 -0700

    powerpc/pseries: Enable HVPIPE event message interrupt

    The hypervisor signals the OS via a Hypervisor Pipe Event external
    interrupt when data is available to be received from the pipe.
    Then the OS  should call RTAS check-exception and provide the input
    Event Mask as defined for the ‘ibm,hvpipe-msg-events’. In response,
    check-exception will return an event log containing an Pipe Events
    message. This message contains the source ID for which this
    message is intended to and the pipe status such as whether the
    payload is pending in the hypervisor or pipe to source is closed.

    If there is any user space process waiting in the wait_queue for
    the payload from this source ID, wake up that process which can
    issue read() to obtain payload with ibm,receive-hvpipe-msg RTAS
    or close FD if the pipe to source is closed.

    The hypervisor has one pipe per partition for all sources and it
    will not deliver another hvpipe event message until the partition
    reads the payload for the previous hvpipe event. So if the source
    ID is not found in the source list, issue the dummy
    ibm,receive-hvpipe-msg RTAS so that pipe will not blocked.

    Register hvpipe event source interrupt based on entries from
    /proc/device-tree//event-sources/ibm,hvpipe-msg-events property.

    Signed-off-by: Haren Myneni <haren@linux.ibm.com>
    Tested-by: Shashank MS <shashank.gowda@in.ibm.com>
    Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
    Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
    Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Link: https://patch.msgid.link/20250909084402.1488456-8-haren@linux.ibm.com

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

Author: Mamatha Inamdar

arch/powerpc/platforms/pseries/papr-hvpipe.c

@@ -22,6 +22,11 @@
 static DEFINE_SPINLOCK(hvpipe_src_list_lock);
 static LIST_HEAD(hvpipe_src_list);
 
+static unsigned char hvpipe_ras_buf[RTAS_ERROR_LOG_MAX];
+static struct workqueue_struct *papr_hvpipe_wq;
+static struct work_struct *papr_hvpipe_work;
+static int hvpipe_check_exception_token;
+
 /*
  * New PowerPC FW provides support for partitions and various
  * sources (Ex: remote hardware management console (HMC)) to
@@ -554,6 +559,117 @@ static long papr_hvpipe_dev_ioctl(struct file *filp, unsigned int ioctl,
 	return ret;
 }
 
+/*
+ * papr_hvpipe_work_fn - called to issue recv HVPIPE RTAS for
+ * sources that are not monitored by user space so that pipe
+ * will not be blocked.
+ */
+static void papr_hvpipe_work_fn(struct work_struct *work)
+{
+	hvpipe_rtas_recv_msg(NULL, 0);
+}
+
+/*
+ * HVPIPE event message IRQ handler.
+ * The hypervisor sends event IRQ if the partition has payload
+ * and generates another event only after payload is read with
+ * recv HVPIPE RTAS.
+ */
+static irqreturn_t hvpipe_event_interrupt(int irq, void *dev_id)
+{
+	struct hvpipe_event_buf *hvpipe_event;
+	struct pseries_errorlog *pseries_log;
+	struct hvpipe_source_info *src_info;
+	struct rtas_error_log *elog;
+	int rc;
+
+	rc = rtas_call(hvpipe_check_exception_token, 6, 1, NULL,
+		RTAS_VECTOR_EXTERNAL_INTERRUPT, virq_to_hw(irq),
+		RTAS_HVPIPE_MSG_EVENTS, 1, __pa(&hvpipe_ras_buf),
+		rtas_get_error_log_max());
+
+	if (rc != 0) {
+		pr_err_ratelimited("unexpected hvpipe-event-notification failed %d\n", rc);
+		return IRQ_HANDLED;
+	}
+
+	elog = (struct rtas_error_log *)hvpipe_ras_buf;
+	if (unlikely(rtas_error_type(elog) != RTAS_TYPE_HVPIPE)) {
+		pr_warn_ratelimited("Unexpected event type %d\n",
+				rtas_error_type(elog));
+		return IRQ_HANDLED;
+	}
+
+	pseries_log = get_pseries_errorlog(elog,
+				PSERIES_ELOG_SECT_ID_HVPIPE_EVENT);
+	hvpipe_event = (struct hvpipe_event_buf *)pseries_log->data;
+
+	/*
+	 * The hypervisor notifies partition when the payload is
+	 * available to read with recv HVPIPE RTAS and it will not
+	 * notify another event for any source until the previous
+	 * payload is read. Means the pipe is blocked in the
+	 * hypervisor until the payload is read.
+	 *
+	 * If the source is ready to accept payload and wakeup the
+	 * corresponding FD. Hold lock and update hvpipe_status
+	 * and this lock is needed in case the user space process
+	 * is in release FD instead of poll() so that release()
+	 * reads the payload to unblock pipe before closing FD.
+	 *
+	 * otherwise (means no other user process waiting for the
+	 * payload, issue recv HVPIPE RTAS (papr_hvpipe_work_fn())
+	 * to unblock pipe.
+	 */
+	spin_lock(&hvpipe_src_list_lock);
+	src_info = hvpipe_find_source(be32_to_cpu(hvpipe_event->srcID));
+	if (src_info) {
+		u32 flags = 0;
+
+		if (hvpipe_event->event_type & HVPIPE_LOST_CONNECTION)
+			flags = HVPIPE_LOST_CONNECTION;
+		else if (hvpipe_event->event_type & HVPIPE_MSG_AVAILABLE)
+			flags = HVPIPE_MSG_AVAILABLE;
+
+		src_info->hvpipe_status |= flags;
+		wake_up(&src_info->recv_wqh);
+		spin_unlock(&hvpipe_src_list_lock);
+	} else {
+		spin_unlock(&hvpipe_src_list_lock);
+		/*
+		 * user space is not waiting on this source. So
+		 * execute receive pipe RTAS so that pipe will not
+		 * be blocked.
+		 */
+		if (hvpipe_event->event_type & HVPIPE_MSG_AVAILABLE)
+			queue_work(papr_hvpipe_wq, papr_hvpipe_work);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int __init enable_hvpipe_IRQ(void)
+{
+	struct device_node *np;
+
+	hvpipe_check_exception_token = rtas_token("check-exception");
+	if (hvpipe_check_exception_token  == RTAS_UNKNOWN_SERVICE)
+		return -ENODEV;
+
+	/* hvpipe events */
+	np = of_find_node_by_path("/event-sources/ibm,hvpipe-msg-events");
+	if (np != NULL) {
+		request_event_sources_irqs(np, hvpipe_event_interrupt,
+					"HPIPE_EVENT");
+		of_node_put(np);
+	} else {
+		pr_err("Can not enable hvpipe event IRQ\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 static const struct file_operations papr_hvpipe_ops = {
 	.unlocked_ioctl	=	papr_hvpipe_dev_ioctl,
 };
@@ -576,12 +692,32 @@ static int __init papr_hvpipe_init(void)
 		!rtas_service_present("ibm,receive-hvpipe-msg"))
 		return -ENODEV;
 
-	ret = misc_register(&papr_hvpipe_dev);
-	if (ret) {
-		pr_err("misc-dev registration failed %d\n", ret);
-		return ret;
+	papr_hvpipe_work = kzalloc(sizeof(struct work_struct), GFP_ATOMIC);
+	if (!papr_hvpipe_work)
+		return -ENOMEM;
+
+	INIT_WORK(papr_hvpipe_work, papr_hvpipe_work_fn);
+
+	papr_hvpipe_wq = alloc_ordered_workqueue("papr hvpipe workqueue", 0);
+	if (!papr_hvpipe_wq) {
+		ret = -ENOMEM;
+		goto out;
 	}
 
-	return 0;
+	ret = enable_hvpipe_IRQ();
+	if (!ret)
+		ret = misc_register(&papr_hvpipe_dev);
+
+	if (!ret) {
+		pr_info("hvpipe feature is enabled\n");
+		return 0;
+	}
+
+	pr_err("hvpipe feature is not enabled %d\n", ret);
+	destroy_workqueue(papr_hvpipe_wq);
+out:
+	kfree(papr_hvpipe_work);
+	papr_hvpipe_work = NULL;
+	return ret;
 }
 machine_device_initcall(pseries, papr_hvpipe_init);

arch/powerpc/platforms/pseries/papr-hvpipe.h

@@ -19,4 +19,18 @@ struct hvpipe_source_info {
 	struct task_struct *tsk;
 };
 
+/*
+ * Source ID Format 0xCCRRQQQQ
+ * CC = indicating value is source type (ex: 0x02 for HMC)
+ * RR = 0x00 (reserved)
+ * QQQQ = 0x0000 – 0xFFFF indicating the source index indetifier
+ */
+struct hvpipe_event_buf {
+	__be32	srcID;		/* Source ID */
+	u8	event_type;	/* 0x01 for hvpipe message available */
+				/* from specified src ID */
+				/* 0x02 for loss of pipe connection */
+				/* with specified src ID */
+};
+
 #endif /* _PAPR_HVPIPE_H */