[PATCH RFC 1/3] x86/pvclock: add setter for pvclock_pvti_cpu0_va

[Joao Martins <joao.m.martins@oracle.com>]

Right now there is only a pvclock_pvti_cpu0_va() which is defined on
kvmclock since:

commit dac16fba6fc5
("x86/vdso: Get pvclock data from the vvar VMA instead of the fixmap")

The only user of this interface so far is kvm. This commit adds a setter
function for the pvti page and moves pvclock_pvti_cpu0_va to pvclock, which
is a more generic place to have it; and would allow other PV clocksources
to use it, such as Xen. 

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 arch/x86/include/asm/pvclock.h | 22 +++++++++++++---------
 arch/x86/kernel/kvmclock.c     |  6 +-----
 arch/x86/kernel/pvclock.c      | 11 +++++++++++
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 66df22b..cfb1bb6 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -4,15 +4,6 @@
 #include <linux/clocksource.h>
 #include <asm/pvclock-abi.h>
 
-#ifdef CONFIG_PARAVIRT_CLOCK
-extern struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
-#else
-static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
-{
-	return NULL;
-}
-#endif
-
 /* some helper functions for xen and kvm pv clock sources */
 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
@@ -101,4 +92,17 @@ struct pvclock_vsyscall_time_info {
 
 #define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
 
+#ifdef CONFIG_PARAVIRT_CLOCK
+void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti);
+struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
+#else
+static inline void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *)
+{
+}
+static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
+{
+	return NULL;
+}
+#endif
+
 #endif /* _ASM_X86_PVCLOCK_H */
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 72cef58..02a5d9e6 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -45,11 +45,6 @@ early_param("no-kvmclock", parse_no_kvmclock);
 static struct pvclock_vsyscall_time_info *hv_clock;
 static struct pvclock_wall_clock wall_clock;
 
-struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
-{
-	return hv_clock;
-}
-
 /*
  * The wallclock is the time of day when we booted. Since then, some time may
  * have elapsed since the hypervisor wrote the data. So we try to account for
@@ -329,6 +324,7 @@ int __init kvm_setup_vsyscall_timeinfo(void)
 		return 1;
 	}
 
+	pvclock_set_pvti_cpu0_va(hv_clock);
 	put_cpu();
 
 	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 99bfc02..da6fbe2 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -25,6 +25,7 @@
 #include <asm/pvclock.h>
 
 static u8 valid_flags __read_mostly = 0;
+static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly;
 
 void pvclock_set_flags(u8 flags)
 {
@@ -140,3 +141,13 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
 
 	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
 }
+
+void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
+{
+	pvti_cpu0_va = pvti;
+}
+
+struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
+{
+	return pvti_cpu0_va;
+}
-- 
2.1.4