[RFC PATCH v2 3/7] x86/kvm, ptp/kvm: Add clocksource ID, set system_counterval_t.cs_id

[Peter Hilber <peter.hilber@opensynergy.com>]

Add a clocksource ID for the x86 kvmclock.

Also, for ptp_kvm, set the recently added struct system_counterval_t member
cs_id to the clocksource ID (x86 kvmclock or Arm Generic Timer). In the
future, this will keep get_device_system_crosststamp() working, when it
will compare the clocksource id in struct system_counterval_t, rather than
the clocksource.

For now, to avoid touching too many subsystems at once, extract the
clocksource ID from the clocksource. The clocksource dereference will be
removed in the following.

Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
---

Notes:
    v2:
    
    - Name clock id according to Thomas Gleixner's mockup.

 arch/x86/kernel/kvmclock.c      | 2 ++
 drivers/ptp/ptp_kvm_common.c    | 2 ++
 include/linux/clocksource_ids.h | 1 +
 3 files changed, 5 insertions(+)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index fb8f52149be9..25d6bf743b03 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -4,6 +4,7 @@
 */
 
 #include <linux/clocksource.h>
+#include <linux/clocksource_ids.h>
 #include <linux/kvm_para.h>
 #include <asm/pvclock.h>
 #include <asm/msr.h>
@@ -160,6 +161,7 @@ struct clocksource kvm_clock = {
 	.rating	= 400,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.id     = CSID_X86_KVM_CLK,
 	.enable	= kvm_cs_enable,
 };
 EXPORT_SYMBOL_GPL(kvm_clock);
diff --git a/drivers/ptp/ptp_kvm_common.c b/drivers/ptp/ptp_kvm_common.c
index 2418977989be..b0b36f135347 100644
--- a/drivers/ptp/ptp_kvm_common.c
+++ b/drivers/ptp/ptp_kvm_common.c
@@ -4,6 +4,7 @@
  *
  * Copyright (C) 2017 Red Hat Inc.
  */
+#include <linux/clocksource.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -47,6 +48,7 @@ static int ptp_kvm_get_time_fn(ktime_t *device_time,
 
 	system_counter->cycles = cycle;
 	system_counter->cs = cs;
+	system_counter->cs_id = cs->id;
 
 	*device_time = timespec64_to_ktime(tspec);
 
diff --git a/include/linux/clocksource_ids.h b/include/linux/clocksource_ids.h
index f8467946e9ee..a4fa3436940c 100644
--- a/include/linux/clocksource_ids.h
+++ b/include/linux/clocksource_ids.h
@@ -8,6 +8,7 @@ enum clocksource_ids {
 	CSID_ARM_ARCH_COUNTER,
 	CSID_X86_TSC_EARLY,
 	CSID_X86_TSC,
+	CSID_X86_KVM_CLK,
 	CSID_MAX,
 };
 
-- 
2.40.1