Patch "[PATCH 127/135] x86/hyperv: Avoid reporting bogus NMI status for Gen2" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

[PATCH 127/135] x86/hyperv: Avoid reporting bogus NMI status for Gen2

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     0127-x86-hyperv-Avoid-reporting-bogus-NMI-status-for-Gen2.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Vitaly Kuznetsov <[email protected]>
Date: Fri, 15 Apr 2016 15:50:32 +0200
Subject: [PATCH 127/135] x86/hyperv: Avoid reporting bogus NMI status for Gen2
instances

[ Upstream commit 1e2ae9ec072f3b7887f456426bc2cf23b80f661a ]

Generation2 instances don't support reporting the NMI status on port 0x61, read from there returns 'ff' and we end up reporting nonsensical PCI error (as there is no PCI bus in these instances) on all NMIs:

NMI: PCI system error (SERR) for reason ff on CPU 0. Dazed and confused, but trying to continue

Fix the issue by overriding x86_platform.get_nmi_reason. Use 'booted on EFI' flag to detect Gen2 instances.

---
 arch/x86/kernel/cpu/mshyperv.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

@@ -152,6 +152,11 @@ static struct clocksource hyperv_cs = {
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+static unsigned char hv_get_nmi_reason(void)
+{
+	return 0;
+}
+
 static void __init ms_hyperv_init_platform(void)
 {
 	/*

@@ -191,6 +196,13 @@ static void __init ms_hyperv_init_platfo
 	machine_ops.crash_shutdown = hv_machine_crash_shutdown;
 #endif
 	mark_tsc_unstable("running on Hyper-V");
+
+	/*
+	 * Generation 2 instances don't support reading the NMI status from
+	 * 0x61 port.
+	 */
+	if (efi_enabled(EFI_BOOT))
+		x86_platform.get_nmi_reason = hv_get_nmi_reason;
 }
 
 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/0038-drivers-hv-cleanup-synic-msrs-if-vmbus-connect-faile.patch queue-4.4/0097-Drivers-hv-vmbus-avoid-infinite-loop-in-init_vp_inde.patch queue-4.4/0118-clocksource-Allow-unregistering-the-watchdog.patch queue-4.4/0099-Drivers-hv-vmbus-don-t-manipulate-with-clocksources-.patch queue-4.4/0127-x86-hyperv-Avoid-reporting-bogus-NMI-status-for-Gen2.patch queue-4.4/0098-Drivers-hv-vmbus-avoid-scheduling-in-interrupt-conte.patch