Linux Virtualization - Nov 2018 - Patch "x86/hyper-v: Enable PIT shutdown quirk" has been added to the 4.19-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 4.19-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 <stable at vger.kernel.org> know about it.

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

From: Michael Kelley <mikelley at microsoft.com>

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

Hi gregkh,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[cannot apply to v4.20-rc3 next-20181119]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system]

url:   
https://github.com/0day-ci/linux/commits/gregkh-linuxfoundation-org/Patch-x86-hyper-v-Enable-PIT-shutdown-quirk-has-been-added-to-the-4-19-stable-tree/20181120-042611
config: i386-randconfig-x019-201846 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   arch/x86/kernel/cpu/mshyperv.c: In function
'ms_hyperv_init_platform':
>> arch/x86/kernel/cpu/mshyperv.c:297:2: error:
'i8253_clear_counter_on_shutdown' undeclared (first use in this
function)
     i8253_clear_counter_on_shutdown = false;
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/cpu/mshyperv.c:297:2: note: each undeclared identifier is
reported only once for each function it appears in

vim +/i8253_clear_counter_on_shutdown +297 arch/x86/kernel/cpu/mshyperv.c

   275	
   276	#if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
   277		machine_ops.shutdown = hv_machine_shutdown;
   278		machine_ops.crash_shutdown = hv_machine_crash_shutdown;
   279	#endif
   280		mark_tsc_unstable("running on Hyper-V");
   281	
   282		/*
   283		 * Generation 2 instances don't support reading the NMI status from
   284		 * 0x61 port.
   285		 */
   286		if (efi_enabled(EFI_BOOT))
   287			x86_platform.get_nmi_reason = hv_get_nmi_reason;
   288	
   289		/*
   290		 * Hyper-V VMs have a PIT emulation quirk such that zeroing the
   291		 * counter register during PIT shutdown restarts the PIT. So it
   292		 * continues to interrupt @18.2 HZ. Setting i8253_clear_counter
   293		 * to false tells pit_shutdown() not to zero the counter so that
   294		 * the PIT really is shutdown. Generation 2 VMs don't have a PIT,
   295		 * and setting this value has no effect.
   296		 */
 > 297		i8253_clear_counter_on_shutdown = false;
   298	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
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Hi gregkh,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[cannot apply to v4.20-rc3 next-20181120]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system]

url:   
https://github.com/0day-ci/linux/commits/gregkh-linuxfoundation-org/Patch-x86-hyper-v-Enable-PIT-shutdown-quirk-has-been-added-to-the-4-19-stable-tree/20181120-042611
config: x86_64-allmodconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All error/warnings (new ones prefixed by >>):
>> arch/x86/kernel/cpu/mshyperv.c:297:9: error: undefined identifier
'i8253_clear_counter_on_shutdown'
   arch/x86/kernel/cpu/mshyperv.c:320:41: warning: symbol
'x86_hyper_ms_hyperv' was not declared. Should it be
static?
>> arch/x86/kernel/cpu/mshyperv.c:297:9: warning: generating address of
non-lvalue (3)
   arch/x86/kernel/cpu/mshyperv.c: In function
'ms_hyperv_init_platform':
   arch/x86/kernel/cpu/mshyperv.c:297:2: error:
'i8253_clear_counter_on_shutdown' undeclared (first use in this
function)
     i8253_clear_counter_on_shutdown = false;
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/cpu/mshyperv.c:297:2: note: each undeclared identifier is
reported only once for each function it appears in

vim +/i8253_clear_counter_on_shutdown +297 arch/x86/kernel/cpu/mshyperv.c

   275	
   276	#if IS_ENABLED(CONFIG_HYPERV) && defined(CONFIG_KEXEC_CORE)
   277		machine_ops.shutdown = hv_machine_shutdown;
   278		machine_ops.crash_shutdown = hv_machine_crash_shutdown;
   279	#endif
   280		mark_tsc_unstable("running on Hyper-V");
   281	
   282		/*
   283		 * Generation 2 instances don't support reading the NMI status from
   284		 * 0x61 port.
   285		 */
   286		if (efi_enabled(EFI_BOOT))
   287			x86_platform.get_nmi_reason = hv_get_nmi_reason;
   288	
   289		/*
   290		 * Hyper-V VMs have a PIT emulation quirk such that zeroing the
   291		 * counter register during PIT shutdown restarts the PIT. So it
   292		 * continues to interrupt @18.2 HZ. Setting i8253_clear_counter
   293		 * to false tells pit_shutdown() not to zero the counter so that
   294		 * the PIT really is shutdown. Generation 2 VMs don't have a PIT,
   295		 * and setting this value has no effect.
   296		 */
 > 297		i8253_clear_counter_on_shutdown = false;
   298	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
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