FAILED: patch "[PATCH] x86/Hyper-V: Trigger crash enlightenment only once during" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 73f26e526f19afb3a06b76b970a76bcac2cafd05 Mon Sep 17 00:00:00 2001
From: Tianyu Lan <[email protected]>
Date: Mon, 6 Apr 2020 08:53:28 -0700
Subject: [PATCH] x86/Hyper-V: Trigger crash enlightenment only once during
system crash.

When a guest VM panics, Hyper-V should be notified only once via the crash synthetic MSRs. Current Linux code might write these crash MSRs twice during a system panic:
1) hyperv_panic/die_event() calling hyperv_report_panic()
2) hv_kmsg_dump() calling hyperv_report_panic_msg()

Fix this by not calling hyperv_report_panic() if a kmsg dump has been successfully registered. The notification will happen later via hyperv_report_panic_msg().

index 00a511f15926..333dad39b1c1 100644
@@ -55,7 +55,13 @@ 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) {
+	/*
+	 * Hyper-V should be notified only once about a panic.  If we will be
+	 * doing hyperv_report_panic_msg() later with kmsg data, don't do
+	 * the notification here.
+	 */
+	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 +74,13 @@ 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);
+	/*
+	 * Hyper-V should be notified only once about a panic.  If we will be
+	 * doing hyperv_report_panic_msg() later with kmsg data, don't do
+	 * the notification here.
+	 */
+	if (!hv_panic_page)
+		hyperv_report_panic(regs, val);
 	return NOTIFY_DONE;
 }
 

This patch builds on 74347a99e73a ("x86/Hyper-V: Unload vmbus channel in hv panic callback") which previously failed to apply. Once that issue was resolved we can grab this patch too.

Thanks,
Sasha