Drivers: hv: vmbus: add special kexec handler

When general-purpose kexec (not kdump) is being performed in Hyper-V guest
the newly booted kernel fails with an MCE error coming from the host. It
is the same error which was fixed in the "Drivers: hv: vmbus: Implement
the protocol for tearing down vmbus state" commit - monitor pages remain
special and when they're being written to (as the new kernel doesn't know
these pages are special) bad things happen. We need to perform some
minimalistic cleanup before booting a new kernel on kexec. To do so we
need to register a special machine_ops.shutdown handler to be executed
before the native_machine_shutdown(). Registering a shutdown notification
handler via the register_reboot_notifier() call is not sufficient as it
happens to early for our purposes. machine_ops is not being exported to
modules (and I don't think we want to export it) so let's do this in
mshyperv.c

The minimalistic cleanup consists of cleaning up clockevents, synic MSRs,
guest os id MSR, and hypercall MSR.

Kdump doesn't require all this stuff as it lives in a separate memory
space.

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 00d5158b4ac7..31748a21d8f9 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1060,6 +1060,17 @@ static struct acpi_driver vmbus_acpi_driver = {
 	},
 };
 
+static void hv_kexec_handler(void)
+{
+	int cpu;
+
+	hv_synic_clockevents_cleanup();
+	vmbus_initiate_unload();
+	for_each_online_cpu(cpu)
+		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
+	hv_cleanup();
+};
+
 static int __init hv_acpi_init(void)
 {
 	int ret, t;
@@ -1092,6 +1103,8 @@ static int __init hv_acpi_init(void)
 	if (ret)
 		goto cleanup;
 
+	hv_setup_kexec_handler(hv_kexec_handler);
+
 	return 0;
 
 cleanup:
@@ -1104,6 +1117,7 @@ static void __exit vmbus_exit(void)
 {
 	int cpu;
 
+	hv_remove_kexec_handler();
 	vmbus_connection.conn_state = DISCONNECTED;
 	hv_synic_clockevents_cleanup();
 	vmbus_disconnect();