3.16.63-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Michael Kelley <mikel...@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 <mikel...@microsoft.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: "gre...@linuxfoundation.org" <gre...@linuxfoundation.org> Cc: "de...@linuxdriverproject.org" <de...@linuxdriverproject.org> Cc: "daniel.lezc...@linaro.org" <daniel.lezc...@linaro.org> Cc: "virtualizat...@lists.linux-foundation.org" <virtualizat...@lists.linux-foundation.org> Cc: "jgr...@suse.com" <jgr...@suse.com> Cc: "akata...@vmware.com" <akata...@vmware.com> Cc: "o...@aepfle.de" <o...@aepfle.de> Cc: "a...@canonical.com" <a...@canonical.com> Cc: vkuznets <vkuzn...@redhat.com> Cc: "jasow...@redhat.com" <jasow...@redhat.com> Cc: "marcelo.ce...@canonical.com" <marcelo.ce...@canonical.com> Cc: KY Srinivasan <k...@microsoft.com> Link: https://lkml.kernel.org/r/1541303219-11142-3-git-send-email-mikel...@microsoft.com [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- 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 @@ -18,6 +18,7 @@ #include <linux/efi.h> #include <linux/interrupt.h> #include <linux/irq.h> +#include <linux/i8253.h> #include <asm/processor.h> #include <asm/hypervisor.h> #include <asm/hyperv.h> @@ -143,6 +144,16 @@ static void __init ms_hyperv_init_platfo no_timer_check = 1; #endif + /* + * 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; + } const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
