[Xen-devel] [PATCH 05/13] x86/hvm: Replace architecture TSC scaling by a common function

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

This patch implements a common function hvm_scale_tsc() to calculate the
scaling of TSC by using TSC scaling information which is collected by
architecture code.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c            | 53 +++++++++++++++++++++++++++++++++++++++
 xen/arch/x86/hvm/svm/svm.c        |  4 +--
 xen/include/asm-x86/hvm/hvm.h     |  1 +
 xen/include/asm-x86/hvm/svm/svm.h |  3 ---
 4 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 63ce4de..2d55a36 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -297,6 +297,59 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
     return 1;
 }
 
+/*
+ * Multiply tsc by a fixed point number represented by ratio.
+ *
+ * The most significant 64-N bits (mult) of ratio represent the
+ * integral part of the fixed point number; the remaining N bits
+ * (frac) represent the fractional part, ie. ratio represents a fixed
+ * point number (mult + frac * 2^(-N)).
+ *
+ * N equals to hvm_funcs.tsc_scaling_ratio_frac_bits.
+ */
+static u64 __scale_tsc(u64 tsc, u64 ratio)
+{
+    u64 mult, frac, mask, _tsc;
+    int width, nr;
+
+    BUG_ON(hvm_funcs.tsc_scaling_ratio_frac_bits >= 64);
+
+    mult  = ratio >> hvm_funcs.tsc_scaling_ratio_frac_bits;
+    mask  = (1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits) - 1;
+    frac  = ratio & mask;
+
+    width = 64 - hvm_funcs.tsc_scaling_ratio_frac_bits;
+    mask  = (1ULL << width) - 1;
+    nr    = hvm_funcs.tsc_scaling_ratio_frac_bits;
+
+    _tsc  = tsc;
+    _tsc *= mult;
+    _tsc += (tsc >> hvm_funcs.tsc_scaling_ratio_frac_bits) * frac;
+
+    while ( nr >= width )
+    {
+        _tsc += (((tsc >> (nr - width)) & mask) * frac) >> (64 - nr);
+        nr   -= width;
+    }
+
+    if ( nr > 0 )
+        _tsc += ((tsc & ((1ULL << nr) - 1)) * frac) >>
+            hvm_funcs.tsc_scaling_ratio_frac_bits;
+
+    return _tsc;
+}
+
+u64 hvm_scale_tsc(struct vcpu *v, u64 tsc)
+{
+    u64 _tsc = tsc;
+    u64 ratio = v->arch.tsc_scaling_ratio;
+
+    if ( ratio != hvm_funcs.default_tsc_scaling_ratio )
+        _tsc = __scale_tsc(ratio, tsc);
+
+    return _tsc;
+}
+
 void hvm_setup_tsc_scaling(struct vcpu *v)
 {
     u64 ratio, khz;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index a7465c6..0984021 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -804,7 +804,7 @@ static void svm_set_tsc_offset(struct vcpu *v, u64 offset, 
u64 at_tsc)
             host_tsc = at_tsc;
         else
             host_tsc = rdtsc();
-        offset = svm_get_tsc_offset(host_tsc, guest_tsc, vcpu_tsc_ratio(v));
+        offset = guest_tsc - hvm_scale_tsc(v, host_tsc);
     }
 
     if ( !nestedhvm_enabled(d) ) {
@@ -965,7 +965,7 @@ static inline void svm_tsc_ratio_save(struct vcpu *v)
 static inline void svm_tsc_ratio_load(struct vcpu *v)
 {
     if ( cpu_has_tsc_ratio && !v->domain->arch.vtsc ) 
-        wrmsrl(MSR_AMD64_TSC_RATIO, vcpu_tsc_ratio(v));
+        wrmsrl(MSR_AMD64_TSC_RATIO, v->arch.tsc_scaling_ratio);
 }
 
 static void svm_ctxt_switch_from(struct vcpu *v)
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 55e7f64..f63fe93 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -261,6 +261,7 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, 
u64 at_tsc);
 u64 hvm_get_guest_tsc_fixed(struct vcpu *v, u64 at_tsc);
 #define hvm_get_guest_tsc(v) hvm_get_guest_tsc_fixed(v, 0)
 
+u64 hvm_scale_tsc(struct vcpu *v, u64 tsc);
 void hvm_setup_tsc_scaling(struct vcpu *v);
 
 int hvm_set_mode(struct vcpu *v, int mode);
diff --git a/xen/include/asm-x86/hvm/svm/svm.h 
b/xen/include/asm-x86/hvm/svm/svm.h
index a4832d9..42aa6e8 100644
--- a/xen/include/asm-x86/hvm/svm/svm.h
+++ b/xen/include/asm-x86/hvm/svm/svm.h
@@ -98,9 +98,6 @@ extern u32 svm_feature_flags;
 #define DEFAULT_TSC_RATIO       0x0000000100000000ULL
 #define MAX_TSC_RATIO           0x000000ffffffffffULL
 #define TSC_RATIO_RSVD_BITS     0xffffff0000000000ULL
-#define TSC_RATIO(g_khz, h_khz) ( (((u64)(g_khz)<<32)/(u64)(h_khz)) & \
-                                  ~TSC_RATIO_RSVD_BITS )
-#define vcpu_tsc_ratio(v)       TSC_RATIO((v)->domain->arch.tsc_khz, cpu_khz)
 
 extern void svm_host_osvw_reset(void);
 extern void svm_host_osvw_init(void);
-- 
2.4.8


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