4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Kelley mikelley@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@microsoft.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: "gregkh@linuxfoundation.org" gregkh@linuxfoundation.org Cc: "devel@linuxdriverproject.org" devel@linuxdriverproject.org Cc: "daniel.lezcano@linaro.org" daniel.lezcano@linaro.org Cc: "virtualization@lists.linux-foundation.org" virtualization@lists.linux-foundation.org Cc: "jgross@suse.com" jgross@suse.com Cc: "akataria@vmware.com" akataria@vmware.com Cc: "olaf@aepfle.de" olaf@aepfle.de Cc: "apw@canonical.com" apw@canonical.com Cc: vkuznets vkuznets@redhat.com Cc: "jasowang@redhat.com" jasowang@redhat.com Cc: "marcelo.cerri@canonical.com" marcelo.cerri@canonical.com Cc: KY Srinivasan kys@microsoft.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1541303219-11142-3-git-send-email-mikelley@microso... 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-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.