Drivers: hv: vmbus: Suspend/resume the synic for hibernation

This is needed when we resume the old kernel from the "current" kernel.

Note: when hv_synic_suspend() and hv_synic_resume() run, all the
non-boot CPUs have been offlined, and interrupts are disabled on CPU0.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index ebd35fc35290..2ef375ce58ac 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -30,6 +30,7 @@
 #include <linux/kdebug.h>
 #include <linux/efi.h>
 #include <linux/random.h>
+#include <linux/syscore_ops.h>
 #include <clocksource/hyperv_timer.h>
 #include "hyperv_vmbus.h"
 
@@ -2086,6 +2087,47 @@ static void hv_crash_handler(struct pt_regs *regs)
         hyperv_cleanup();
 };
 
+static int hv_synic_suspend(void)
+{
+        /*
+         * When we reach here, all the non-boot CPUs have been offlined, and
+         * the stimers on them have been unbound in hv_synic_cleanup() ->
+         * hv_stimer_cleanup() -> clockevents_unbind_device().
+         *
+         * hv_synic_suspend() only runs on CPU0 with interrupts disabled. Here
+         * we do not unbind the stimer on CPU0 because: 1) it's unnecessary
+         * because the interrupts remain disabled between syscore_suspend()
+         * and syscore_resume(): see create_image() and resume_target_kernel();
+         * 2) the stimer on CPU0 is automatically disabled later by
+         * syscore_suspend() -> timekeeping_suspend() -> tick_suspend() -> ...
+         * -> clockevents_shutdown() -> ... -> hv_ce_shutdown(); 3) a warning
+         * would be triggered if we call clockevents_unbind_device(), which
+         * may sleep, in an interrupts-disabled context. So, we intentionally
+         * don't call hv_stimer_cleanup(0) here.
+         */
+
+        hv_synic_disable_regs(0);
+
+        return 0;
+}
+
+static void hv_synic_resume(void)
+{
+        hv_synic_enable_regs(0);
+
+        /*
+         * Note: we don't need to call hv_stimer_init(0), because the timer
+         * on CPU0 is not unbound in hv_synic_suspend(), and the timer is
+         * automatically re-enabled in timekeeping_resume().
+         */
+}
+
+/* The callbacks run only on CPU0, with irqs_disabled. */
+static struct syscore_ops hv_synic_syscore_ops = {
+        .suspend = hv_synic_suspend,
+        .resume = hv_synic_resume,
+};
+
 static int __init hv_acpi_init(void)
 {
         int ret, t;
@@ -2116,6 +2158,8 @@ static int __init hv_acpi_init(void)
         hv_setup_kexec_handler(hv_kexec_handler);
         hv_setup_crash_handler(hv_crash_handler);
 
+        register_syscore_ops(&hv_synic_syscore_ops);
+
         return 0;
 
 cleanup:
@@ -2128,6 +2172,8 @@ static void __exit vmbus_exit(void)
 {
         int cpu;
 
+        unregister_syscore_ops(&hv_synic_syscore_ops);
+
         hv_remove_kexec_handler();
         hv_remove_crash_handler();
         vmbus_connection.conn_state = DISCONNECTED;