From e2768eaa1ca4fbb7b778da5615cce3dd310352e6 Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Wed, 24 Jan 2018 14:23:32 +0100
Subject: [PATCH] x86/hyperv: Add a function to read both TSC and TSC page
 value simulateneously
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This is going to be used from KVM code where both TSC and TSC page value
are needed.

Nothing is supposed to use the function when Hyper-V code is compiled out,
just BUG().

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: devel@linuxdriverproject.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Cathy Avery <cavery@redhat.com>
Cc: Mohammed Gamal <mmorsy@redhat.com>
Link: https://lkml.kernel.org/r/20180124132337.30138-3-vkuznets@redhat.com
---
 arch/x86/hyperv/hv_init.c       |  1 +
 arch/x86/include/asm/mshyperv.h | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 21f9d53d9f00..1a6c63f721bc 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -37,6 +37,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
 	return tsc_pg;
 }
+EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 
 static u64 read_hv_clock_tsc(struct clocksource *arg)
 {
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 8bf450b13d9f..6b1d4ea78270 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -325,9 +325,10 @@ static inline void hyperv_setup_mmu_ops(void) {}
 
 #ifdef CONFIG_HYPERV_TSCPAGE
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
-static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+				       u64 *cur_tsc)
 {
-	u64 scale, offset, cur_tsc;
+	u64 scale, offset;
 	u32 sequence;
 
 	/*
@@ -358,7 +359,7 @@ static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
 
 		scale = READ_ONCE(tsc_pg->tsc_scale);
 		offset = READ_ONCE(tsc_pg->tsc_offset);
-		cur_tsc = rdtsc_ordered();
+		*cur_tsc = rdtsc_ordered();
 
 		/*
 		 * Make sure we read sequence after we read all other values
@@ -368,7 +369,14 @@ static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
 
 	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
 
-	return mul_u64_u64_shr(cur_tsc, scale, 64) + offset;
+	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
+}
+
+static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
+{
+	u64 cur_tsc;
+
+	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
 }
 
 #else
@@ -376,5 +384,12 @@ static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
 	return NULL;
 }
+
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+				       u64 *cur_tsc)
+{
+	BUG();
+	return U64_MAX;
+}
 #endif
 #endif