linux-kernel - [PATCH v2 0/2] i8253: Fix PIT shutdown quirk on Hyper-V

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Date:   Sun, 4 Nov 2018 03:48:50 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "jgross@...e.com" <jgross@...e.com>,
        "akataria@...are.com" <akataria@...are.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        vkuznets <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        KY Srinivasan <kys@...rosoft.com>
CC:     Michael Kelley <mikelley@...rosoft.com>
Subject: [PATCH v2 0/2] i8253: Fix PIT shutdown quirk on Hyper-V

pit_shutdown() doesn't work on Hyper-V because of a quirk in the
PIT emulation. This problem exists in all versions of Hyper-V and
had not been noticed previously. When the counter register is set
to zero, the emulated PIT continues to interrupt @18.2 HZ.

Account for this quirk by adding a global variable in the i8253
code that controls whether the counter register is zero'ed. Then
in Hyper-V initialization code, override the default setting so
the counter register is not zero'ed.

Changes in v2:
* Instead of a function call to check if running on Hyper-V,
use a global variable to control whether the counter register
is zero'ed. [Juergen Gross & Thomas Gleixner]

Michael Kelley (2):
  i8253: Add support for PIT shutdown quirk
  x86/hyper-v: Enable PIT shutdown quirk

 arch/x86/kernel/cpu/mshyperv.c | 11 +++++++++++
 drivers/clocksource/i8253.c    | 14 ++++++++++++--
 include/linux/i8253.h          |  1 +
 3 files changed, 24 insertions(+), 2 deletions(-)

-- 
1.8.3.1