linux-kernel - [patch V2 08/17] clocksource: Add common vdso clock mode storage

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Date:   Fri, 07 Feb 2020 13:38:55 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, John Stultz <john.stultz@...aro.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        James Hogan <jhogan@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>, Andrei Vagin <avagin@...il.com>
Subject: [patch V2 08/17] clocksource: Add common vdso clock mode storage

From: Thomas Gleixner <tglx@...utronix.de>

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@...utronix.de>
---
V2: Fix the unused variable warning and s/mode/clock_mode/ - Christophe
---
 include/linux/clocksource.h |   12 +++++++++++-
 kernel/time/clocksource.c   |    9 +++++++++
 kernel/time/vsyscall.c      |   10 ++++++++--
 lib/vdso/Kconfig            |    3 +++
 lib/vdso/gettimeofday.c     |   13 +++++++++++--
 5 files changed, 42 insertions(+), 5 deletions(-)

--- 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);
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -928,6 +928,15 @@ int __clocksource_register_scale(struct
 
 	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);
 
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -71,13 +71,19 @@ void update_vsyscall(struct timekeeper *
 {
 	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];
--- 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
--- 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 v
 
 	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
 		}
 		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);