clocksource: Add common vdso clock mode storage

All architectures which use the generic VDSO code have their own storage
for the VDSO clock mode. That's pointless and just requires duplicate code.

Provide generic storage for it. The new Kconfig symbol is intermediate and
will be removed once all architectures are converted over.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200207124403.028046322@linutronix.de

5 files changed, 42 insertions, 5 deletions

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 2c4574b517d2..6d5ed1b4d24d 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -23,10 +23,19 @@
 struct clocksource;
 struct module;
 
-#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
+#if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
+    defined(CONFIG_GENERIC_VDSO_CLOCK_MODE)
 #include <asm/clocksource.h>
 #endif
 
+enum vdso_clock_mode {
+	VDSO_CLOCKMODE_NONE,
+#ifdef CONFIG_GENERIC_VDSO_CLOCK_MODE
+	VDSO_ARCH_CLOCKMODES,
+#endif
+	VDSO_CLOCKMODE_MAX,
+};
+
 /**
  * struct clocksource - hardware abstraction for a free running counter
  *	Provides mostly state-free accessors to the underlying hardware.
@@ -97,6 +106,7 @@ struct clocksource {
 	const char		*name;
 	struct list_head	list;
 	int			rating;
+	enum vdso_clock_mode	vdso_clock_mode;
 	unsigned long		flags;
 
 	int			(*enable)(struct clocksource *cs);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 428beb69426a..7cb09c4cf21c 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -928,6 +928,15 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
 
 	clocksource_arch_init(cs);
 
+#ifdef CONFIG_GENERIC_VDSO_CLOCK_MODE
+	if (cs->vdso_clock_mode < 0 ||
+	    cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
+		pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
+			cs->name, cs->vdso_clock_mode);
+		cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
+	}
+#endif
+
 	/* Initialize mult/shift and max_idle_ns */
 	__clocksource_update_freq_scale(cs, scale, freq);
 
diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
index 9577c89179cd..f9a5178c69bb 100644
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -71,13 +71,19 @@ void update_vsyscall(struct timekeeper *tk)
 {
 	struct vdso_data *vdata = __arch_get_k_vdso_data();
 	struct vdso_timestamp *vdso_ts;
+	s32 clock_mode;
 	u64 nsec;
 
 	/* copy vsyscall data */
 	vdso_write_begin(vdata);
 
-	vdata[CS_HRES_COARSE].clock_mode	= __arch_get_clock_mode(tk);
-	vdata[CS_RAW].clock_mode		= __arch_get_clock_mode(tk);
+#ifdef CONFIG_GENERIC_VDSO_CLOCK_MODE
+	clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
+#else
+	clock_mode = __arch_get_clock_mode(tk);
+#endif
+	vdata[CS_HRES_COARSE].clock_mode	= clock_mode;
+	vdata[CS_RAW].clock_mode		= clock_mode;
 
 	/* CLOCK_REALTIME also required for time() */
 	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
diff --git a/lib/vdso/Kconfig b/lib/vdso/Kconfig
index d883ac299508..d9f43c84fcc6 100644
--- a/lib/vdso/Kconfig
+++ b/lib/vdso/Kconfig
@@ -30,4 +30,7 @@ config GENERIC_VDSO_TIME_NS
 	  Selected by architectures which support time namespaces in the
 	  VDSO
 
+config GENERIC_VDSO_CLOCK_MODE
+	bool
+
 endif
diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index 5804e4e168e7..3f2d8b859130 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -7,6 +7,7 @@
 #include <linux/time.h>
 #include <linux/kernel.h>
 #include <linux/hrtimer_defs.h>
+#include <linux/clocksource.h>
 #include <vdso/datapage.h>
 #include <vdso/helpers.h>
 
@@ -64,10 +65,14 @@ static int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
 
 	do {
 		seq = vdso_read_begin(vd);
+		if (IS_ENABLED(CONFIG_GENERIC_VDSO_CLOCK_MODE) &&
+		    vd->clock_mode == VDSO_CLOCKMODE_NONE)
+			return -1;
 		cycles = __arch_get_hw_counter(vd->clock_mode);
 		ns = vdso_ts->nsec;
 		last = vd->cycle_last;
-		if (unlikely((s64)cycles < 0))
+		if (!IS_ENABLED(CONFIG_GENERIC_VDSO_CLOCK_MODE) &&
+		    unlikely((s64)cycles < 0))
 			return -1;
 
 		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
@@ -132,10 +137,14 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
 		}
 		smp_rmb();
 
+		if (IS_ENABLED(CONFIG_GENERIC_VDSO_CLOCK_MODE) &&
+		    vd->clock_mode == VDSO_CLOCKMODE_NONE)
+			return -1;
 		cycles = __arch_get_hw_counter(vd->clock_mode);
 		ns = vdso_ts->nsec;
 		last = vd->cycle_last;
-		if (unlikely((s64)cycles < 0))
+		if (!IS_ENABLED(CONFIG_GENERIC_VDSO_CLOCK_MODE) &&
+		    unlikely((s64)cycles < 0))
 			return -1;
 
 		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);