[Xen-devel] [PATCH v2 10/14] 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 scale TSC by
using TSC scaling information collected by architecture code.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c        | 18 +++++++++--
 xen/arch/x86/hvm/svm/svm.c    | 12 --------
 xen/arch/x86/time.c           |  2 +-
 xen/include/asm-x86/hvm/hvm.h |  3 +-
 xen/include/asm-x86/math64.h  | 70 +++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 88 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 52a0ef8..1e3d89f 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -302,6 +302,20 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
     return 1;
 }
 
+u64 hvm_scale_tsc(const struct vcpu *v, u64 tsc)
+{
+    u64 ratio = v->arch.hvm_vcpu.tsc_scaling_ratio;
+
+    if ( !hvm_funcs.tsc_scaling_supported ||
+         ratio == hvm_funcs.default_tsc_scaling_ratio )
+        return tsc;
+
+    BUG_ON(hvm_funcs.tsc_scaling_ratio_frac_bits >= 64 ||
+           hvm_funcs.tsc_scaling_ratio_frac_bits == 0);
+
+    return mul_u64_u64_shr(tsc, ratio, hvm_funcs.tsc_scaling_ratio_frac_bits);
+}
+
 void hvm_setup_tsc_scaling(struct vcpu *v)
 {
     u64 ratio;
@@ -339,7 +353,7 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, 
u64 at_tsc)
     {
         tsc = at_tsc ?: rdtsc();
         if ( cpu_has_tsc_ratio )
-            tsc = hvm_funcs.scale_tsc(v, tsc);
+            tsc = hvm_scale_tsc(v, tsc);
     }
 
     delta_tsc = guest_tsc - tsc;
@@ -371,7 +385,7 @@ u64 hvm_get_guest_tsc_fixed(struct vcpu *v, uint64_t at_tsc)
     {
         tsc = at_tsc ?: rdtsc();
         if ( cpu_has_tsc_ratio )
-            tsc = hvm_funcs.scale_tsc(v, tsc);
+            tsc = hvm_scale_tsc(v, tsc);
     }
 
     return tsc + v->arch.hvm_vcpu.cache_tsc_offset;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index d291327..9e28245 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -804,16 +804,6 @@ static uint64_t scale_tsc(uint64_t host_tsc, uint64_t 
ratio)
     return scaled_host_tsc;
 }
 
-static uint64_t svm_scale_tsc(struct vcpu *v, uint64_t tsc)
-{
-    struct domain *d = v->domain;
-
-    if ( !cpu_has_tsc_ratio || d->arch.vtsc )
-        return tsc;
-
-    return scale_tsc(tsc, v->arch.hvm_vcpu.tsc_scaling_ratio);
-}
-
 static uint64_t svm_get_tsc_offset(uint64_t host_tsc, uint64_t guest_tsc,
     uint64_t ratio)
 {
@@ -2275,8 +2265,6 @@ static struct hvm_function_table __initdata 
svm_function_table = {
     .nhvm_intr_blocked = nsvm_intr_blocked,
     .nhvm_hap_walk_L1_p2m = nsvm_hap_walk_L1_p2m,
 
-    .scale_tsc            = svm_scale_tsc,
-
     .default_tsc_scaling_ratio   = DEFAULT_TSC_RATIO,
     .max_tsc_scaling_ratio       = ~TSC_RATIO_RSVD_BITS,
     .tsc_scaling_ratio_frac_bits = 32,
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index d4a94eb..2277158 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -817,7 +817,7 @@ static void __update_vcpu_system_time(struct vcpu *v, int 
force)
     {
         if ( is_hvm_domain(d) && cpu_has_tsc_ratio )
         {
-            tsc_stamp            = hvm_funcs.scale_tsc(v, t->local_tsc_stamp);
+            tsc_stamp            = hvm_scale_tsc(v, t->local_tsc_stamp);
             _u.tsc_to_system_mul = d->arch.vtsc_to_ns.mul_frac;
             _u.tsc_shift         = d->arch.vtsc_to_ns.shift;
         }
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index e74524e..8fc59d5 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -225,8 +225,6 @@ struct hvm_function_table {
     bool_t (*altp2m_vcpu_emulate_ve)(struct vcpu *v);
     int (*altp2m_vcpu_emulate_vmfunc)(struct cpu_user_regs *regs);
 
-    uint64_t (*scale_tsc)(struct vcpu *v, uint64_t tsc);
-
     /* Architecture function to setup TSC scaling ratio */
     void (*setup_tsc_scaling)(struct vcpu *v);
 };
@@ -264,6 +262,7 @@ 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(const 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/math64.h b/xen/include/asm-x86/math64.h
index 9af6aee..c6a472b 100644
--- a/xen/include/asm-x86/math64.h
+++ b/xen/include/asm-x86/math64.h
@@ -27,4 +27,74 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 
divisor)
     return rl.ll;
 }
 
+/*
+ * Multiply two 64-bit unsigned integers a and b. The most and least
+ * significant 64 bits of the 128-bit result are returned through hi
+ * and lo respectively.
+ */
+static inline void mul64(u64 *lo, u64 *hi, u64 a, u64 b)
+{
+    typedef union {
+        u64 ll;
+        struct {
+            u32 low, high;
+        } l;
+    } LL;
+    LL rl, rm, rn, rh, a0, b0;
+    u64 c;
+
+    a0.ll = a;
+    b0.ll = b;
+
+    rl.ll = (u64)a0.l.low * b0.l.low;
+    rm.ll = (u64)a0.l.low * b0.l.high;
+    rn.ll = (u64)a0.l.high * b0.l.low;
+    rh.ll = (u64)a0.l.high * b0.l.high;
+
+    c = (u64)rl.l.high + rm.l.low + rn.l.low;
+    rl.l.high = c;
+    c >>= 32;
+    c = c + rm.l.high + rn.l.high + rh.l.low;
+    rh.l.low = c;
+    rh.l.high += (u32)(c >> 32);
+
+    *lo = rl.ll;
+    *hi = rh.ll;
+}
+
+/*
+ * Right shift a 128-bit unsigned integer by n bits. The most and
+ * least significant 64 bits of the 128-bit integer are passed through
+ * hi and lo respectively. The most and least significant 64 bits of
+ * the result are also returned through hi and lo respectively.
+ */
+static inline void rshift128(u64 *lo, u64 *hi, unsigned int n)
+{
+    u64 h;
+    if ( !n )
+        return;
+    h = *hi >> (n & 63);
+    if ( n >= 64 )
+    {
+        *hi = 0;
+        *lo = h;
+    }
+    else
+    {
+        *lo = (*lo >> n) | (*hi << (64 - n));
+        *hi = h;
+    }
+}
+
+/*
+ * (a * mul) >> n
+ */
+static inline u64 mul_u64_u64_shr(u64 a, u64 mul, unsigned int n)
+{
+    u64 lo, hi;
+    mul64(&lo, &hi, a, mul);
+    rshift128(&lo, &hi, n);
+    return lo;
+}
+
 #endif
-- 
2.6.3


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