[PATCH RFC 2/6] x86/hyper-v: add a function to read both TSC and TSC page value simulateneously

[Vitaly Kuznetsov]

This is going to be used from KVM code were we need to get both
TSC and TSC page value.

When Hyper-V code is compiled out just return rdtsc(), this will allow us
to avoid ugly ifdefs in non-Hyper-V code.

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/include/asm/mshyperv.h | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 5400add2885b..2611d2c49f27 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -323,9 +323,10 @@ 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;
 
        /*
@@ -356,7 +357,7 @@ 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
@@ -366,7 +367,14 @@ 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
@@ -374,5 +382,13 @@ 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)
+{
+       *cur_tsc = rdtsc();
+
+       return cur_tsc;
+}
 #endif
 #endif
-- 
2.14.3

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