From dc899971a1b7754f6171e6f1232365b864f96eef Mon Sep 17 00:00:00 2001 From: Ky Srinivasan Date: Thu, 20 May 2010 12:54:06 -0600 Subject: [PATCH] Staging: hyperv: add clocksource driver This patch is a clocksource implementation suitable for guests hosted on HyperV. Time keeping in Linux guests hosted on HyperV is unstable. This clocksource driver fixes the problem. This driver uses the hyperv detection code integrated into the kernel. Signed-off-by: K. Y. Srinivasan Cc: Hank Janssen Cc: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/staging/hv/Makefile | 2 +- drivers/staging/hv/hv_timesource.c | 101 +++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+), 1 deletion(-) create mode 100644 drivers/staging/hv/hv_timesource.c diff --git a/drivers/staging/hv/Makefile b/drivers/staging/hv/Makefile index 1866f80a45d3..b63515c20f5f 100644 --- a/drivers/staging/hv/Makefile +++ b/drivers/staging/hv/Makefile @@ -1,4 +1,4 @@ -obj-$(CONFIG_HYPERV) += hv_vmbus.o +obj-$(CONFIG_HYPERV) += hv_vmbus.o hv_timesource.o obj-$(CONFIG_HYPERV_STORAGE) += hv_storvsc.o obj-$(CONFIG_HYPERV_BLOCK) += hv_blkvsc.o obj-$(CONFIG_HYPERV_NET) += hv_netvsc.o diff --git a/drivers/staging/hv/hv_timesource.c b/drivers/staging/hv/hv_timesource.c new file mode 100644 index 000000000000..a7ee533303b4 --- /dev/null +++ b/drivers/staging/hv/hv_timesource.c @@ -0,0 +1,101 @@ +/* + * A clocksource for Linux running on HyperV. + * + * + * Copyright (C) 2010, Novell, Inc. + * Author : K. Y. Srinivasan + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for more + * details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define HV_CLOCK_SHIFT 22 + +static cycle_t read_hv_clock(struct clocksource *arg) +{ + cycle_t current_tick; + /* + * Read the partition counter to get the current tick count. This count + * is set to 0 when the partition is created and is incremented in + * 100 nanosecond units. + */ + rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick); + return current_tick; +} + +static struct clocksource hyperv_cs = { + .name = "hyperv_clocksource", + .rating = 400, /* use this when running on Hyperv*/ + .read = read_hv_clock, + .mask = CLOCKSOURCE_MASK(64), + /* + * The time ref counter in HyperV is in 100ns units. + * The definition of mult is: + * mult/2^shift = ns/cyc = 100 + * mult = (100 << shift) + */ + .mult = (100 << HV_CLOCK_SHIFT), + .shift = HV_CLOCK_SHIFT, +}; + +static const struct dmi_system_id __initconst +hv_timesource_dmi_table[] __maybe_unused = { + { + .ident = "Hyper-V", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"), + DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"), + DMI_MATCH(DMI_BOARD_NAME, "Virtual Machine"), + }, + }, + { }, +}; +MODULE_DEVICE_TABLE(dmi, hv_timesource_dmi_table); + +static const struct pci_device_id __initconst +hv_timesource_pci_table[] __maybe_unused = { + { PCI_DEVICE(0x1414, 0x5353) }, /* VGA compatible controller */ + { 0 } +}; +MODULE_DEVICE_TABLE(pci, hv_timesource_pci_table); + + +static int __init init_hv_clocksource(void) +{ + if ((x86_hyper != &x86_hyper_ms_hyperv) || + !(ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)) + return -ENODEV; + + if (!dmi_check_system(hv_timesource_dmi_table)) + return -ENODEV; + + printk(KERN_INFO "Registering HyperV clock source\n"); + return clocksource_register(&hyperv_cs); +} + +module_init(init_hv_clocksource); +MODULE_DESCRIPTION("HyperV based clocksource"); +MODULE_AUTHOR("K. Y. Srinivasan "); +MODULE_LICENSE("GPL");