powerpc/pseries: HVPIPE changes to support migration

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

commit 6d84f85
Author: Haren Myneni <haren@linux.ibm.com>
Date:   Tue Sep 9 01:44:01 2025 -0700

    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 <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/20250909084402.1488456-10-haren@linux.ibm.com

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

Author: Mamatha Inamdar

arch/powerpc/platforms/pseries/mobility.c

@@ -27,6 +27,7 @@
 #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;
@@ -752,6 +753,7 @@ static int pseries_migrate_partition(u64 handle)
 	 * 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)
@@ -778,6 +780,7 @@ static int pseries_migrate_partition(u64 handle)
 
 out:
 	vas_migration_handler(VAS_RESUME);
+	hvpipe_migration_handler(HVPIPE_RESUME);
 
 	return ret;
 }

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

@@ -27,6 +27,7 @@ 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;
+static bool hvpipe_feature;
 
 /*
  * New PowerPC FW provides support for partitions and various
@@ -233,6 +234,12 @@ static ssize_t papr_hvpipe_handle_write(struct file *file,
 	unsigned long ret, len;
 	__be64 *area_be;
 
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
+
 	if (!src_info)
 		return -EIO;
 
@@ -323,6 +330,12 @@ static ssize_t papr_hvpipe_handle_read(struct file *file,
 	struct papr_hvpipe_hdr hdr;
 	long ret;
 
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
+
 	if (!src_info)
 		return -EIO;
 
@@ -399,6 +412,13 @@ static __poll_t papr_hvpipe_handle_poll(struct file *filp,
 {
 	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;
 
@@ -539,6 +559,12 @@ static long papr_hvpipe_dev_ioctl(struct file *filp, unsigned int ioctl,
 	u32 srcID;
 	long ret;
 
+	/*
+	 * Return -ENXIO during migration
+	 */
+	if (!hvpipe_feature)
+		return -ENXIO;
+
 	if (get_user(srcID, argp))
 		return -EFAULT;
 
@@ -697,6 +723,44 @@ static int __init enable_hvpipe_IRQ(void)
 	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,
 };
@@ -740,6 +804,7 @@ static int __init papr_hvpipe_init(void)
 
 	if (!ret) {
 		pr_info("hvpipe feature is enabled\n");
+		hvpipe_feature = true;
 		return 0;
 	}
 

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

@@ -11,6 +11,11 @@
 
 #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;
@@ -33,4 +38,5 @@ struct hvpipe_event_buf {
 				/* with specified src ID */
 };
 
+void hvpipe_migration_handler(int action);
 #endif /* _PAPR_HVPIPE_H */