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Subject[PATCH 3/4] x86/Hyper-V: Trigger crash enlightenment only once during system crash.
Date
From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Hyper-V expects guest only triggers crash enlightenment.
The second crash notify will be ignored by Hyper-V.

Current code may trigger crash enlightenment during system
panic twice.
1) The enlightenment is triggered in hyperv_panic/die_event()
via hyperv_report_panic().
2) hv_kmsg_dump() reports kmsg to host via hyperv_report_panic_msg().

Fix it. If kmsg dump is registered successfully, just report
kmsg via hyperv_report_panic_msg() and not report register values
via hyperv_report_panic().

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
drivers/hv/vmbus_drv.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index b043efea092a..1787d6246251 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -55,7 +55,12 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,

vmbus_initiate_unload(true);

- if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+ /*
+ * Crash notify only can be triggered once. If crash notify
+ * message is available, just report kmsg to crash buffer.
+ */
+ if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE
+ && !hv_panic_page) {
regs = current_pt_regs();
hyperv_report_panic(regs, val);
}
@@ -68,7 +73,12 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val,
struct die_args *die = (struct die_args *)args;
struct pt_regs *regs = die->regs;

- hyperv_report_panic(regs, val);
+ /*
+ * Crash notify only can be triggered once. If crash notify
+ * message is available, just report kmsg to crash buffer.
+ */
+ if (!hv_panic_page)
+ hyperv_report_panic(regs, val);
return NOTIFY_DONE;
}

--
2.14.5
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