Patch "x86/hyper-v: Enable PIT shutdown quirk" has been added to the 4.14-stable tree

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

    x86/hyper-v: Enable PIT shutdown quirk

to the 4.14-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:
     x86-hyper-v-enable-pit-shutdown-quirk.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.


From 1de72c706488b7be664a601cf3843bd01e327e58 Mon Sep 17 00:00:00 2001
From: Michael Kelley <redacted>
Date: Sun, 4 Nov 2018 03:48:57 +0000
Subject: x86/hyper-v: Enable PIT shutdown quirk

From: Michael Kelley <redacted>

commit 1de72c706488b7be664a601cf3843bd01e327e58 upstream.

Hyper-V emulation of the PIT has a quirk such that the normal PIT shutdown
path doesn't work, because clearing the counter register restarts the
timer.

Disable the counter clearing on PIT shutdown.

Signed-off-by: Michael Kelley <redacted>
Signed-off-by: Thomas Gleixner <redacted>
Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "devel@linuxdriverproject.org" <redacted>
Cc: "daniel.lezcano@linaro.org" <redacted>
Cc: "virtualization@lists.linux-foundation.org" <redacted>
Cc: "jgross@suse.com" <jgross@suse.com>
Cc: "akataria@vmware.com" <redacted>
Cc: "olaf@aepfle.de" <redacted>
Cc: "apw@canonical.com" <apw@canonical.com>
Cc: vkuznets <vkuznets@redhat.com>
Cc: "jasowang@redhat.com" <redacted>
Cc: "marcelo.cerri@canonical.com" <redacted>
Cc: KY Srinivasan <kys@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1541303219-11142-3-git-send-email-mikelley@microsoft.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/cpu/mshyperv.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c

@@ -20,6 +20,7 @@
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/kexec.h>
+#include <linux/i8253.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
 #include <asm/hyperv.h>

@@ -243,6 +244,16 @@ static void __init ms_hyperv_init_platfo
 	if (efi_enabled(EFI_BOOT))
 		x86_platform.get_nmi_reason = hv_get_nmi_reason;
 
+	/*
+	 * Hyper-V VMs have a PIT emulation quirk such that zeroing the
+	 * counter register during PIT shutdown restarts the PIT. So it
+	 * continues to interrupt @18.2 HZ. Setting i8253_clear_counter
+	 * to false tells pit_shutdown() not to zero the counter so that
+	 * the PIT really is shutdown. Generation 2 VMs don't have a PIT,
+	 * and setting this value has no effect.
+	 */
+	i8253_clear_counter_on_shutdown = false;
+
 #if IS_ENABLED(CONFIG_HYPERV)
 	/*
 	 * Setup the hook to get control post apic initialization.

Patches currently in stable-queue which might be from mikelley@microsoft.com are

queue-4.14/x86-hyper-v-enable-pit-shutdown-quirk.patch
queue-4.14/clockevents-drivers-i8253-add-support-for-pit-shutdown-quirk.patch