x86/vdso: Move VDSO clocksource state tracking to callback

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>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>  (Hyper-V parts)
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> (VDSO parts)
Acked-by: Juergen Gross <jgross@suse.com> (Xen parts)
Link: https://lkml.kernel.org/r/20200207124402.934519777@linutronix.de

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/include/asm/clocksource.h b/arch/x86/include/asm/clocksource.h
index dc4cfc888d6d..2450d6e02a5d 100644
--- 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 */