Merge tag 'powerpc-6.7-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:

 - Fix a bug where heavy VAS (accelerator) usage could race with
   partition migration and prevent the migration from completing.

 - Update MAINTAINERS to add Aneesh & Naveen.

Thanks to Haren Myneni.

* tag 'powerpc-6.7-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  MAINTAINERS: powerpc: Add Aneesh & Naveen
  powerpc/pseries/vas: Migration suspend waits for no in-progress open windows

Author: torvalds

MAINTAINERS

@@ -12189,6 +12189,8 @@ LINUX FOR POWERPC (32-BIT AND 64-BIT)
 M:	Michael Ellerman <mpe@ellerman.id.au>
 R:	Nicholas Piggin <npiggin@gmail.com>
 R:	Christophe Leroy <christophe.leroy@csgroup.eu>
+R:	Aneesh Kumar K.V <aneesh.kumar@kernel.org>
+R:	Naveen N. Rao <naveen.n.rao@linux.ibm.com>
 L:	linuxppc-dev@lists.ozlabs.org
 S:	Supported
 W:	https://github.com/linuxppc/wiki/wiki

arch/powerpc/platforms/pseries/vas.c

@@ -385,11 +385,15 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 	 * same fault IRQ is not freed by the OS before.
 	 */
 	mutex_lock(&vas_pseries_mutex);
-	if (migration_in_progress)
+	if (migration_in_progress) {
 		rc = -EBUSY;
-	else
+	} else {
 		rc = allocate_setup_window(txwin, (u64 *)&domain[0],
 				   cop_feat_caps->win_type);
+		if (!rc)
+			caps->nr_open_wins_progress++;
+	}
+
 	mutex_unlock(&vas_pseries_mutex);
 	if (rc)
 		goto out;
@@ -404,18 +408,29 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 		goto out_free;
 
 	txwin->win_type = cop_feat_caps->win_type;
-	mutex_lock(&vas_pseries_mutex);
+
 	/*
+	 * The migration SUSPEND thread sets migration_in_progress and
+	 * closes all open windows from the list. But the window is
+	 * added to the list after open and modify HCALLs. So possible
+	 * that migration_in_progress is set before modify HCALL which
+	 * may cause some windows are still open when the hypervisor
+	 * initiates the migration.
+	 * So checks the migration_in_progress flag again and close all
+	 * open windows.
+	 *
 	 * Possible to lose the acquired credit with DLPAR core
 	 * removal after the window is opened. So if there are any
 	 * closed windows (means with lost credits), do not give new
 	 * window to user space. New windows will be opened only
 	 * after the existing windows are reopened when credits are
 	 * available.
 	 */
-	if (!caps->nr_close_wins) {
+	mutex_lock(&vas_pseries_mutex);
+	if (!caps->nr_close_wins && !migration_in_progress) {
 		list_add(&txwin->win_list, &caps->list);
 		caps->nr_open_windows++;
+		caps->nr_open_wins_progress--;
 		mutex_unlock(&vas_pseries_mutex);
 		vas_user_win_add_mm_context(&txwin->vas_win.task_ref);
 		return &txwin->vas_win;
@@ -433,6 +448,12 @@ static struct vas_window *vas_allocate_window(int vas_id, u64 flags,
 	 */
 	free_irq_setup(txwin);
 	h_deallocate_vas_window(txwin->vas_win.winid);
+	/*
+	 * Hold mutex and reduce nr_open_wins_progress counter.
+	 */
+	mutex_lock(&vas_pseries_mutex);
+	caps->nr_open_wins_progress--;
+	mutex_unlock(&vas_pseries_mutex);
 out:
 	atomic_dec(&cop_feat_caps->nr_used_credits);
 	kfree(txwin);
@@ -937,14 +958,14 @@ int vas_migration_handler(int action)
 	struct vas_caps *vcaps;
 	int i, rc = 0;
 
+	pr_info("VAS migration event %d\n", action);
+
 	/*
 	 * NX-GZIP is not enabled. Nothing to do for migration.
 	 */
 	if (!copypaste_feat)
 		return rc;
 
-	mutex_lock(&vas_pseries_mutex);
-
 	if (action == VAS_SUSPEND)
 		migration_in_progress = true;
 	else
@@ -990,12 +1011,27 @@ int vas_migration_handler(int action)
 
 		switch (action) {
 		case VAS_SUSPEND:
+			mutex_lock(&vas_pseries_mutex);
 			rc = reconfig_close_windows(vcaps, vcaps->nr_open_windows,
 							true);
+			/*
+			 * Windows are included in the list after successful
+			 * open. So wait for closing these in-progress open
+			 * windows in vas_allocate_window() which will be
+			 * done if the migration_in_progress is set.
+			 */
+			while (vcaps->nr_open_wins_progress) {
+				mutex_unlock(&vas_pseries_mutex);
+				msleep(10);
+				mutex_lock(&vas_pseries_mutex);
+			}
+			mutex_unlock(&vas_pseries_mutex);
 			break;
 		case VAS_RESUME:
+			mutex_lock(&vas_pseries_mutex);
 			atomic_set(&caps->nr_total_credits, new_nr_creds);
 			rc = reconfig_open_windows(vcaps, new_nr_creds, true);
+			mutex_unlock(&vas_pseries_mutex);
 			break;
 		default:
 			/* should not happen */
@@ -1011,8 +1047,9 @@ int vas_migration_handler(int action)
 			goto out;
 	}
 
+	pr_info("VAS migration event (%d) successful\n", action);
+
 out:
-	mutex_unlock(&vas_pseries_mutex);
 	return rc;
 }
 

arch/powerpc/platforms/pseries/vas.h

@@ -91,6 +91,8 @@ struct vas_cop_feat_caps {
 struct vas_caps {
 	struct vas_cop_feat_caps caps;
 	struct list_head list;	/* List of open windows */
+	int nr_open_wins_progress;	/* Number of open windows in */
+					/* progress. Used in migration */
 	int nr_close_wins;	/* closed windows in the hypervisor for DLPAR */
 	int nr_open_windows;	/* Number of successful open windows */
 	u8 feat;		/* Feature type */