linux-kernel - [PATCH v3 1/4] powerpc/mobility: wait for memory transfer to complete

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Date:   Mon, 27 Jun 2022 15:53:44 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     wim@...ux-watchdog.org, linux@...ck-us.net, mpe@...erman.id.au,
        benh@...nel.crashing.org, paulus@...ba.org, nathanl@...ux.ibm.com,
        haren@...ux.vnet.ibm.com, npiggin@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-watchdog@...r.kernel.org
Subject: [PATCH v3 1/4] powerpc/mobility: wait for memory transfer to complete

In pseries_migration_partition(), loop until the memory transfer is
complete. This way the calling drmgr process will not exit earlier,
allowing callbacks to be run only once the migration is fully completed.

If reading the VASI state is done after the hypervisor has completed the
migration, the HCALL is returning H_PARAMETER. We can safely assume that
the memory transfer is achieved if this happens.

This will also allow to manage the NMI watchdog state in the next commits.

Reviewed-by: Nathan Lynch <nathanl@...ux.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/platforms/pseries/mobility.c | 42 +++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index 78f3f74c7056..907a779074d6 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -427,6 +427,43 @@ static int wait_for_vasi_session_suspending(u64 handle)
 	return ret;
 }
 
+static void wait_for_vasi_session_completed(u64 handle)
+{
+	unsigned long state = 0;
+	int ret;
+
+	pr_info("waiting for memory transfert to complete...\n");
+
+	/*
+	 * Wait for transition from H_VASI_RESUMED to H_VASI_COMPLETED.
+	 */
+	while (true) {
+		ret = poll_vasi_state(handle, &state);
+
+		/*
+		 * If the memory transfer is already complete and the migration
+		 * has been cleaned up by the hypervisor, H_PARAMETER is return,
+		 * which is translate in EINVAL by poll_vasi_state().
+		 */
+		if (ret == -EINVAL || (!ret && state == H_VASI_COMPLETED)) {
+			pr_info("memory transfert completed.\n");
+			break;
+		}
+
+		if (ret) {
+			pr_err("H_VASI_STATE return error (%d)\n", ret);
+			break;
+		}
+
+		if (state != H_VASI_RESUMED) {
+			pr_err("unexpected H_VASI_STATE result %lu\n", state);
+			break;
+		}
+
+		msleep(500);
+	}
+}
+
 static void prod_single(unsigned int target_cpu)
 {
 	long hvrc;
@@ -673,9 +710,10 @@ static int pseries_migrate_partition(u64 handle)
 	vas_migration_handler(VAS_SUSPEND);
 
 	ret = pseries_suspend(handle);
-	if (ret == 0)
+	if (ret == 0) {
 		post_mobility_fixup();
-	else
+		wait_for_vasi_session_completed(handle);
+	} else
 		pseries_cancel_migration(handle, ret);
 
 	vas_migration_handler(VAS_RESUME);
-- 
2.36.1