Drivers: hv: vmbus: add special crash handler

Full kernel hang is observed when kdump kernel starts after a crash. This
hang happens in vmbus_negotiate_version() function on
wait_for_completion() as Hyper-V host (Win2012R2 in my testing) never
responds to CHANNELMSG_INITIATE_CONTACT as it thinks the connection is
already established. We need to perform some mandatory minimalistic
cleanup before we start new kernel.

Reported-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 31748a2..1ed9b32 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1071,6 +1071,18 @@ static void hv_kexec_handler(void)
 	hv_cleanup();
 };
 
+static void hv_crash_handler(struct pt_regs *regs)
+{
+	vmbus_initiate_unload();
+	/*
+	 * In crash handler we can't schedule synic cleanup for all CPUs,
+	 * doing the cleanup for current CPU only. This should be sufficient
+	 * for kdump.
+	 */
+	hv_synic_cleanup(NULL);
+	hv_cleanup();
+};
+
 static int __init hv_acpi_init(void)
 {
 	int ret, t;
@@ -1104,6 +1116,7 @@ static int __init hv_acpi_init(void)
 		goto cleanup;
 
 	hv_setup_kexec_handler(hv_kexec_handler);
+	hv_setup_crash_handler(hv_crash_handler);
 
 	return 0;
 
@@ -1118,6 +1131,7 @@ static void __exit vmbus_exit(void)
 	int cpu;
 
 	hv_remove_kexec_handler();
+	hv_remove_crash_handler();
 	vmbus_connection.conn_state = DISCONNECTED;
 	hv_synic_clockevents_cleanup();
 	vmbus_disconnect();