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 4.19-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-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 1de72c706488b7be664a601cf3843bd01e327e58 Mon Sep 17 00:00:00 2001
From: Michael Kelley <[email protected]>
Date: Sun, 4 Nov 2018 03:48:57 +0000
Subject: x86/hyper-v: Enable PIT shutdown quirk
From: Michael Kelley <[email protected]>
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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]"
<[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: vkuznets <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: KY Srinivasan <[email protected]>
Cc: [email protected]
Link:
https://lkml.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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-tlfs.h>
@@ -285,6 +286,16 @@ 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 [email protected] are
queue-4.19/x86-hyper-v-enable-pit-shutdown-quirk.patch
queue-4.19/clockevents-drivers-i8253-add-support-for-pit-shutdown-quirk.patch
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