From 465dda9d320d1cb9424f1015b0520ec4c4f0d279 Mon Sep 17 00:00:00 2001
From: Haren Myneni <haren@linux.ibm.com>
Date: Thu, 22 Sep 2022 01:27:07 -0700
Subject: [PATCH] powerpc/pseries: Move vas_migration_handler early during
 migration

References: bsc#1204799 ltc#200177
Patch-mainline: v6.1-rc1
Git-commit: 465dda9d320d1cb9424f1015b0520ec4c4f0d279

When the migration is initiated, the hypervisor changes VAS
mappings as part of pre-migration event. Then the OS gets the
migration event which closes all VAS windows before the migration
starts. NX generates continuous faults until windows are closed
and the user space can not differentiate these NX faults coming
from the actual migration. So to reduce this time window, close
VAS windows first in pseries_migrate_partition().

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/d8efade91dda831c9ed4abb226dab627da594c5f.camel@linux.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/platforms/pseries/mobility.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index c92c78332303..634fac5db3f9 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -740,11 +740,19 @@ static int pseries_migrate_partition(u64 handle)
 #ifdef CONFIG_PPC_WATCHDOG
 	factor = nmi_wd_lpm_factor;
 #endif
+	/*
+	 * When the migration is initiated, the hypervisor changes VAS
+	 * mappings to prepare before OS gets the notification and
+	 * closes all VAS windows. NX generates continuous faults during
+	 * this time and the user space can not differentiate these
+	 * faults from the migration event. So reduce this time window
+	 * by closing VAS windows at the beginning of this function.
+	 */
+	vas_migration_handler(VAS_SUSPEND);
+
 	ret = wait_for_vasi_session_suspending(handle);
 	if (ret)
-		return ret;
-
-	vas_migration_handler(VAS_SUSPEND);
+		goto out;
 
 	if (factor)
 		watchdog_nmi_set_timeout_pct(factor);
@@ -765,6 +773,7 @@ static int pseries_migrate_partition(u64 handle)
 	if (factor)
 		watchdog_nmi_set_timeout_pct(0);
 
+out:
 	vas_migration_handler(VAS_RESUME);
 
 	return ret;
-- 
2.35.3