[PATCH v3 4/8] 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, get_device_system_crosststamp() 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:
    v3:
    
    - Omit redundant clocksource_ids.h include (Andy Shevchenko).
    
    v2:
    
    - Name clock id according to Thomas Gleixner's mockup.

 arch/x86/kernel/kvmclock.c      | 1 +
 drivers/ptp/ptp_kvm_common.c    | 2 ++
 include/linux/clocksource_ids.h | 1 +
 3 files changed, 4 insertions(+)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 5bb395551c44..2f1bbf730f45 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -160,6 +160,7 @@ 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