powerpc/pseries: HVPIPE changes to support migration

The hypervisor assigns one pipe per partition for all sources and
assigns new pipe after migration. Also the partition ID that is
used by source as its target ID may be changed after the migration.
So disable hvpipe during SUSPEND event with ‘hvpipe enable’ system
parameter value = 0 and enable it after migration during RESUME
event with hvpipe enable’ system parameter value = 1.

The user space calls such as ioctl()/ read() / write() / poll()
returns -ENXIO between SUSPEND and RESUME events. The user space
process can close FD and reestablish connection with new FD after
migration if needed (Example: source IDs are changed).

Signed-off-by: Haren Myneni <[e-mail]>
Tested-by: Shashank MS <[e-mail]>
Reviewed-by: Mahesh Salgaonkar <[e-mail]>
Reviewed-by: Tyrel Datwyler <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/platforms/pseries/mobility.c

···
 #include <asm/rtas.h>
 #include "pseries.h"
 #include "vas.h"	/* vas_migration_handler() */
+#include "papr-hvpipe.h"	/* hvpipe_migration_handler() */
 #include "../../kernel/cacheinfo.h"
 
 static struct kobject *mobility_kobj;
···
 	 * by closing VAS windows at the beginning of this function.
 	 */
 	vas_migration_handler(VAS_SUSPEND);
+	hvpipe_migration_handler(HVPIPE_SUSPEND);
 
 	ret = wait_for_vasi_session_suspending(handle);
 	if (ret)
···
 
 out:
 	vas_migration_handler(VAS_RESUME);
+	hvpipe_migration_handler(HVPIPE_RESUME);
 
 	return ret;
 }

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

···
 static struct workqueue_struct *papr_hvpipe_wq;
 static struct work_struct *papr_hvpipe_work;
 static int hvpipe_check_exception_token;
+static bool hvpipe_feature;
 
 /*
  * New PowerPC FW provides support for partitions and various
···
 	unsigned long ret, len;
 	__be64 *area_be;
 
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
+
 	if (!src_info)
 		return -EIO;
 
···
 	struct papr_hvpipe_hdr hdr;
 	long ret;
 
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
+
 	if (!src_info)
 		return -EIO;
 
···
 		struct poll_table_struct *wait)
 {
 	struct hvpipe_source_info *src_info = filp->private_data;
+
+	/*
+	 * HVPIPE is disabled during SUSPEND and enabled after migration.
+	 * So return POLLRDHUP during migration
+	 */
+	if (!hvpipe_feature)
+		return POLLRDHUP;
 
 	if (!src_info)
 		return POLLNVAL;
···
 	u32 __user *argp = (void __user *)arg;
 	u32 srcID;
 	long ret;
+
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
 
 	if (get_user(srcID, argp))
 		return -EFAULT;
···
 	return 0;
 }
 
+void hvpipe_migration_handler(int action)
+{
+	pr_info("hvpipe migration event %d\n", action);
+
+	/*
+	 * HVPIPE is not used (Failed to create /dev/papr-hvpipe).
+	 * So nothing to do for migration.
+	 */
+	if (!papr_hvpipe_work)
+		return;
+
+	switch (action) {
+	case HVPIPE_SUSPEND:
+		if (hvpipe_feature) {
+			/*
+			 * Disable hvpipe_feature to the user space.
+			 * It will be enabled with RESUME event.
+			 */
+			hvpipe_feature = false;
+			/*
+			 * set system parameter hvpipe 'disable'
+			 */
+			set_hvpipe_sys_param(0);
+		}
+		break;
+	case HVPIPE_RESUME:
+		/*
+		 * set system parameter hvpipe 'enable'
+		 */
+		if (!set_hvpipe_sys_param(1))
+			hvpipe_feature = true;
+		else
+			pr_err("hvpipe is not enabled after migration\n");
+
+		break;
+	}
+}
+
 static const struct file_operations papr_hvpipe_ops = {
 	.unlocked_ioctl	=	papr_hvpipe_dev_ioctl,
 };
···
 
 	if (!ret) {
 		pr_info("hvpipe feature is enabled\n");
+		hvpipe_feature = true;
 		return 0;
 	}
 

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

···
 
 #define	HVPIPE_HDR_LEN	sizeof(struct papr_hvpipe_hdr)
 
+enum hvpipe_migrate_action {
+	HVPIPE_SUSPEND,
+	HVPIPE_RESUME,
+};
+
 struct hvpipe_source_info {
 	struct list_head list;	/* list of sources */
 	u32 srcID;
···
 				/* with specified src ID */
 };
 
+void hvpipe_migration_handler(int action);
 #endif /* _PAPR_HVPIPE_H */