[patch 08/15] x86/vdso: Move VDSO clocksource state tracking to callback

[Thomas Gleixner <tglx@linutronix.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.

X86 abuses the function which retrieves the architecture specific clock
mode storage to mark the clocksource as used in the VDSO. That's silly
because this is invoked on every tick when the VDSO data is updated.

Move this functionality to the clocksource::enable() callback so it gets
invoked once when the clocksource is installed. This allows to make the
clock mode storage generic.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
---
 arch/x86/entry/vdso/vma.c            |    4 ++++
 arch/x86/include/asm/clocksource.h   |   12 ++++++++++++
 arch/x86/include/asm/mshyperv.h      |    2 ++
 arch/x86/include/asm/vdso/vsyscall.h |   10 +---------
 arch/x86/include/asm/vgtod.h         |    6 ------
 arch/x86/kernel/kvmclock.c           |    7 +++++++
 arch/x86/kernel/tsc.c                |   32 ++++++++++++++++++++------------
 arch/x86/xen/time.c                  |   17 ++++++++++++-----
 drivers/clocksource/hyperv_timer.c   |    7 +++++++
 9 files changed, 65 insertions(+), 32 deletions(-)

--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -38,6 +38,8 @@ struct vdso_data *arch_get_vdso_data(voi
 }
 #undef EMIT_VVAR
 
+unsigned int vclocks_used __read_mostly;
+
 #if defined(CONFIG_X86_64)
 unsigned int __read_mostly vdso64_enabled = 1;
 #endif
@@ -445,6 +447,8 @@ static __init int vdso_setup(char *s)
 
 static int __init init_vdso(void)
 {
+	BUILD_BUG_ON(VCLOCK_MAX >= 32);
+
 	init_vdso_image(&vdso_image_64);
 
 #ifdef CONFIG_X86_X32_ABI
--- a/arch/x86/include/asm/clocksource.h
+++ b/arch/x86/include/asm/clocksource.h
@@ -14,4 +14,16 @@ struct arch_clocksource_data {
 	int vclock_mode;
 };
 
+extern unsigned int vclocks_used;
+
+static inline bool vclock_was_used(int vclock)
+{
+	return READ_ONCE(vclocks_used) & (1U << vclock);
+}
+
+static inline void vclocks_set_used(unsigned int which)
+{
+	WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << which));
+}
+
 #endif /* _ASM_X86_CLOCKSOURCE_H */
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -47,6 +47,8 @@ typedef int (*hyperv_fill_flush_list_fun
 	wrmsrl(HV_X64_MSR_REFERENCE_TSC, val)
 #define hv_set_clocksource_vdso(val) \
 	((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
+#define hv_enable_vdso_clocksource() \
+	vclocks_set_used(VCLOCK_HVCLOCK);
 #define hv_get_raw_timer() rdtsc_ordered()
 
 void hyperv_callback_vector(void);
--- a/arch/x86/include/asm/vdso/vsyscall.h
+++ b/arch/x86/include/asm/vdso/vsyscall.h
@@ -10,8 +10,6 @@
 #include <asm/vgtod.h>
 #include <asm/vvar.h>
 
-int vclocks_used __read_mostly;
-
 DEFINE_VVAR(struct vdso_data, _vdso_data);
 /*
  * Update the vDSO data page to keep in sync with kernel timekeeping.
@@ -26,13 +24,7 @@ struct vdso_data *__x86_get_k_vdso_data(
 static __always_inline
 int __x86_get_clock_mode(struct timekeeper *tk)
 {
-	int vclock_mode = tk->tkr_mono.clock->archdata.vclock_mode;
-
-	/* Mark the new vclock used. */
-	BUILD_BUG_ON(VCLOCK_MAX >= 32);
-	WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << vclock_mode));
-
-	return vclock_mode;
+	return tk->tkr_mono.clock->archdata.vclock_mode;
 }
 #define __arch_get_clock_mode __x86_get_clock_mode
 
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -15,10 +15,4 @@ typedef u64 gtod_long_t;
 typedef unsigned long gtod_long_t;
 #endif
 
-extern int vclocks_used;
-static inline bool vclock_was_used(int vclock)
-{
-	return READ_ONCE(vclocks_used) & (1 << vclock);
-}
-
 #endif /* _ASM_X86_VGTOD_H */
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -159,12 +159,19 @@ bool kvm_check_and_clear_guest_paused(vo
 	return ret;
 }
 
+static int kvm_cs_enable(struct clocksource *cs)
+{
+	vclocks_set_used(VCLOCK_PVCLOCK);
+	return 0;
+}
+
 struct clocksource kvm_clock = {
 	.name	= "kvm-clock",
 	.read	= kvm_clock_get_cycles,
 	.rating	= 400,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.enable	= kvm_cs_enable,
 };
 EXPORT_SYMBOL_GPL(kvm_clock);
 
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1108,17 +1108,24 @@ static void tsc_cs_tick_stable(struct cl
 		sched_clock_tick_stable();
 }
 
+static int tsc_cs_enable(struct clocksource *cs)
+{
+	vclocks_set_used(VCLOCK_TSC);
+	return 0;
+}
+
 /*
  * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
  */
 static struct clocksource clocksource_tsc_early = {
-	.name                   = "tsc-early",
-	.rating                 = 299,
-	.read                   = read_tsc,
-	.mask                   = CLOCKSOURCE_MASK(64),
-	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+	.name			= "tsc-early",
+	.rating			= 299,
+	.read			= read_tsc,
+	.mask			= CLOCKSOURCE_MASK(64),
+	.flags			= CLOCK_SOURCE_IS_CONTINUOUS |
 				  CLOCK_SOURCE_MUST_VERIFY,
-	.archdata               = { .vclock_mode = VCLOCK_TSC },
+	.archdata		= { .vclock_mode = VCLOCK_TSC },
+	.enable			= tsc_cs_enable,
 	.resume			= tsc_resume,
 	.mark_unstable		= tsc_cs_mark_unstable,
 	.tick_stable		= tsc_cs_tick_stable,
@@ -1131,14 +1138,15 @@ static struct clocksource clocksource_ts
  * been found good.
  */
 static struct clocksource clocksource_tsc = {
-	.name                   = "tsc",
-	.rating                 = 300,
-	.read                   = read_tsc,
-	.mask                   = CLOCKSOURCE_MASK(64),
-	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+	.name			= "tsc",
+	.rating			= 300,
+	.read			= read_tsc,
+	.mask			= CLOCKSOURCE_MASK(64),
+	.flags			= CLOCK_SOURCE_IS_CONTINUOUS |
 				  CLOCK_SOURCE_VALID_FOR_HRES |
 				  CLOCK_SOURCE_MUST_VERIFY,
-	.archdata               = { .vclock_mode = VCLOCK_TSC },
+	.archdata		= { .vclock_mode = VCLOCK_TSC },
+	.enable			= tsc_cs_enable,
 	.resume			= tsc_resume,
 	.mark_unstable		= tsc_cs_mark_unstable,
 	.tick_stable		= tsc_cs_tick_stable,
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -145,12 +145,19 @@ static struct notifier_block xen_pvclock
 	.notifier_call = xen_pvclock_gtod_notify,
 };
 
+static int xen_cs_enable(struct clocksource *cs)
+{
+	vclocks_set_used(VCLOCK_PVCLOCK);
+	return 0;
+}
+
 static struct clocksource xen_clocksource __read_mostly = {
-	.name = "xen",
-	.rating = 400,
-	.read = xen_clocksource_get_cycles,
-	.mask = ~0,
-	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
+	.name	= "xen",
+	.rating	= 400,
+	.read	= xen_clocksource_get_cycles,
+	.mask	= CLOCKSOURCE_MASK(64),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.enable = xen_cs_enable,
 };
 
 /*
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -330,12 +330,19 @@ static u64 read_hv_sched_clock_tsc(void)
 	return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
 }
 
+static int hv_cs_enable(struct clocksource *cs)
+{
+	hv_enable_vdso_clocksource();
+	return 0;
+}
+
 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
 	.rating	= 400,
 	.read	= read_hv_clock_tsc,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.enable = hv_cs_enable,
 };
 
 static u64 notrace read_hv_clock_msr(struct clocksource *arg)