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Subject[PATCH v5 2/9] Drivers: hv: vmbus: Suspend/resume the synic for hibernation
Date
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>
---
drivers/hv/vmbus_drv.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index ebd35fc..2ef375c 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;
--
1.8.3.1
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