[PATCH v5 2/3] hv: export current Hyper-V clocksource

[Vitaly Kuznetsov]

As a preparation to implementing Hyper-V PTP device supporting
.getcrosststamp we need to export a reference to the current Hyper-V
clocksource in use (MSR or TSC page).

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/hyperv/hv_init.c       | 13 +++++++++----
 arch/x86/include/asm/mshyperv.h |  3 +++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index b371d0e..c224b7d 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -99,6 +99,9 @@ static struct clocksource hyperv_cs_msr = {
 };
 
 static void *hypercall_pg;
+struct clocksource *hyperv_cs;
+EXPORT_SYMBOL_GPL(hyperv_cs);
+
 /*
  * This function is to be invoked early in the boot sequence after the
  * hypervisor has been detected.
@@ -141,10 +144,10 @@ void hyperv_init(void)
                union hv_x64_msr_hypercall_contents tsc_msr;
 
                tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
-               if (!tsc_pg) {
-                       clocksource_register_hz(&hyperv_cs_msr, 
NSEC_PER_SEC/100);
-                       return;
-               }
+               if (!tsc_pg)
+                       goto register_msr_cs;
+
+               hyperv_cs = &hyperv_cs_tsc;
 
                rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 
@@ -161,6 +164,8 @@ void hyperv_init(void)
         * the partition counter.
         */
 
+register_msr_cs:
+       hyperv_cs = &hyperv_cs_msr;
        if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
                clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
 }
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index f8dc370..d54833d 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -3,6 +3,7 @@
 
 #include <linux/types.h>
 #include <linux/interrupt.h>
+#include <linux/clocksource.h>
 #include <asm/hyperv.h>
 
 /*
@@ -168,6 +169,8 @@ void hv_setup_crash_handler(void (*handler)(struct pt_regs 
*regs));
 void hv_remove_crash_handler(void);
 
 #if IS_ENABLED(CONFIG_HYPERV)
+extern struct clocksource *hyperv_cs;
+
 void hyperv_init(void);
 void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);
-- 
2.9.3