ptp/kvm, arm_arch_timer: Set system_counterval_t.cs_id to constant

Identify the clocksources used by ptp_kvm by setting the clocksource ID
enum constants. This avoids dereferencing struct clocksource. Once the
system_counterval_t.cs member will be removed, this will also avoid the
need to obtain clocksource pointers from kvm_arch_ptp_get_crosststamp().

The clocksource IDs are associated to timestamps requested from the KVM
hypervisor, so the proper clocksource ID is known at the ptp_kvm request
site.

While at it, also make the ptp_kvm_get_time_fn() 'ret' variable type int as
that's what the function return value is.

Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240201010453.2212371-6-peter.hilber@opensynergy.com

Author: peter-hilber-at-opensynergy-dot-com

drivers/clocksource/arm_arch_timer.c

@@ -1807,7 +1807,8 @@ TIMER_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
 #endif
 
 int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *ts,
-				 struct clocksource **cs)
+				 struct clocksource **cs,
+				 enum clocksource_ids *cs_id)
 {
 	struct arm_smccc_res hvc_res;
 	u32 ptp_counter;
@@ -1833,6 +1834,8 @@ int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *ts,
 		*cycle = (u64)hvc_res.a2 << 32 | hvc_res.a3;
 	if (cs)
 		*cs = &clocksource_counter;
+	if (cs_id)
+		*cs_id = CSID_ARM_ARCH_COUNTER;
 
 	return 0;
 }

drivers/ptp/ptp_kvm_arm.c

@@ -28,5 +28,5 @@ void kvm_arch_ptp_exit(void)
 
 int kvm_arch_ptp_get_clock(struct timespec64 *ts)
 {
-	return kvm_arch_ptp_get_crosststamp(NULL, ts, NULL);
+	return kvm_arch_ptp_get_crosststamp(NULL, ts, NULL, NULL);
 }

drivers/ptp/ptp_kvm_common.c

@@ -4,7 +4,6 @@
  *
  * Copyright (C) 2017 Red Hat Inc.
  */
-#include <linux/clocksource.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -29,15 +28,16 @@ static int ptp_kvm_get_time_fn(ktime_t *device_time,
 			       struct system_counterval_t *system_counter,
 			       void *ctx)
 {
-	long ret;
-	u64 cycle;
+	enum clocksource_ids cs_id;
 	struct timespec64 tspec;
 	struct clocksource *cs;
+	u64 cycle;
+	int ret;
 
 	spin_lock(&kvm_ptp_lock);
 
 	preempt_disable_notrace();
-	ret = kvm_arch_ptp_get_crosststamp(&cycle, &tspec, &cs);
+	ret = kvm_arch_ptp_get_crosststamp(&cycle, &tspec, &cs, &cs_id);
 	if (ret) {
 		spin_unlock(&kvm_ptp_lock);
 		preempt_enable_notrace();
@@ -48,7 +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;
+	system_counter->cs_id = cs_id;
 
 	*device_time = timespec64_to_ktime(tspec);
 

drivers/ptp/ptp_kvm_x86.c

@@ -93,7 +93,8 @@ int kvm_arch_ptp_get_clock(struct timespec64 *ts)
 }
 
 int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
-			      struct clocksource **cs)
+			      struct clocksource **cs,
+			      enum clocksource_ids *cs_id)
 {
 	struct pvclock_vcpu_time_info *src;
 	unsigned int version;
@@ -124,6 +125,7 @@ int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
 	} while (pvclock_read_retry(src, version));
 
 	*cs = &kvm_clock;
+	*cs_id = CSID_X86_KVM_CLK;
 
 	return 0;
 }

include/linux/ptp_kvm.h

@@ -8,6 +8,7 @@
 #ifndef _PTP_KVM_H_
 #define _PTP_KVM_H_
 
+#include <linux/clocksource_ids.h>
 #include <linux/types.h>
 
 struct timespec64;
@@ -17,6 +18,7 @@ int kvm_arch_ptp_init(void);
 void kvm_arch_ptp_exit(void);
 int kvm_arch_ptp_get_clock(struct timespec64 *ts);
 int kvm_arch_ptp_get_crosststamp(u64 *cycle,
-		struct timespec64 *tspec, struct clocksource **cs);
+		struct timespec64 *tspec, struct clocksource **cs,
+		enum clocksource_ids *cs_id);
 
 #endif /* _PTP_KVM_H_ */