[tip:x86/vdso] x86/hyperv: Implement hv_get_tsc_page()

[tip-bot for Vitaly Kuznetsov <tipbot@zytor.com>]

Commit-ID:  bd2a9adaadb8defcaf6c284bca7ff41634105f51
Gitweb:     http://git.kernel.org/tip/bd2a9adaadb8defcaf6c284bca7ff41634105f51
Author:     Vitaly Kuznetsov <vkuznets@redhat.com>
AuthorDate: Fri, 3 Mar 2017 14:21:40 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 11 Mar 2017 14:47:28 +0100

x86/hyperv: Implement hv_get_tsc_page()

To use Hyper-V TSC page clocksource from vDSO we need to make tsc_pg
available. Implement hv_get_tsc_page() and add CONFIG_HYPERV_TSCPAGE to
make #ifdef-s simple.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20170303132142.25595-2-vkuznets@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/hyperv/hv_init.c       | 9 +++++++--
 arch/x86/include/asm/mshyperv.h | 8 ++++++++
 drivers/hv/Kconfig              | 3 +++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 8bef70e..bb1ea58 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -27,10 +27,15 @@
 #include <linux/clockchips.h>
 
 
-#ifdef CONFIG_X86_64
+#ifdef CONFIG_HYPERV_TSCPAGE
 
 static struct ms_hyperv_tsc_page *tsc_pg;
 
+struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+	return tsc_pg;
+}
+
 static u64 read_hv_clock_tsc(struct clocksource *arg)
 {
 	u64 current_tick;
@@ -139,7 +144,7 @@ void hyperv_init(void)
 	/*
 	 * Register Hyper-V specific clocksource.
 	 */
-#ifdef CONFIG_X86_64
+#ifdef CONFIG_HYPERV_TSCPAGE
 	if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
 		union hv_x64_msr_hypercall_contents tsc_msr;
 
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 7c9c895..d324dce 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -176,4 +176,12 @@ void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);
 void hyperv_cleanup(void);
 #endif
+#ifdef CONFIG_HYPERV_TSCPAGE
+struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
+#else
+static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+	return NULL;
+}
+#endif
 #endif
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 0403b51..c29cd53 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -7,6 +7,9 @@ config HYPERV
 	  Select this option to run Linux as a Hyper-V client operating
 	  system.
 
+config HYPERV_TSCPAGE
+       def_bool HYPERV && X86_64
+
 config HYPERV_UTILS
 	tristate "Microsoft Hyper-V Utilities driver"
 	depends on HYPERV && CONNECTOR && NLS