[Xen-devel] [PATCH v5 3/6] 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>
---
Changes in v5:
 * Drop "Reviewed-by" from Kevin Tian and Boris Ostrovsky and "Acked-by" 
   from Jan Beulich because of following changes.
 * Rewrite 64-bit integer arithmetic in hvm_scale_tsc() by inlined assembly.
 * Change the first argument of hvm_scale_tsc() from 'const struct vcpu *' 
   to 'const struct domain *' because it does not relied on vcpu.
---
 xen/arch/x86/hvm/hvm.c        | 21 +++++++++++++++++++--
 xen/arch/x86/hvm/svm/svm.c    |  8 --------
 xen/arch/x86/time.c           |  3 +--
 xen/include/asm-x86/hvm/hvm.h |  3 +--
 4 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index b239bdb..c6a6198 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -321,6 +321,23 @@ u64 hvm_get_tsc_scaling_ratio(u32 gtsc_khz)
     return ratio > hvm_funcs.tsc_scaling.max_ratio ? 0 : ratio;
 }
 
+u64 hvm_scale_tsc(const struct domain *d, u64 tsc)
+{
+    u64 ratio = d->arch.hvm_domain.tsc_scaling_ratio;
+    u64 dummy;
+
+    if ( ratio == hvm_default_tsc_scaling_ratio )
+        return tsc;
+
+    /* tsc = (tsc * ratio) >> hvm_funcs.tsc_scaling.ratio_frac_bits */
+    asm (
+        "mulq %3; shrdq %2,%1,%0"
+        : "+a" (tsc), "=d" (dummy)
+        : "c" (hvm_funcs.tsc_scaling.ratio_frac_bits), "rm" (ratio) );
+
+    return tsc;
+}
+
 void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
 {
     uint64_t tsc;
@@ -335,7 +352,7 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, 
u64 at_tsc)
     {
         tsc = at_tsc ?: rdtsc();
         if ( hvm_tsc_scaling_supported )
-            tsc = hvm_funcs.tsc_scaling.scale_tsc(v, tsc);
+            tsc = hvm_scale_tsc(v->domain, tsc);
     }
 
     delta_tsc = guest_tsc - tsc;
@@ -367,7 +384,7 @@ u64 hvm_get_guest_tsc_fixed(struct vcpu *v, uint64_t at_tsc)
     {
         tsc = at_tsc ?: rdtsc();
         if ( hvm_tsc_scaling_supported )
-            tsc = hvm_funcs.tsc_scaling.scale_tsc(v, tsc);
+            tsc = hvm_scale_tsc(v->domain, 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 1136937..dbdfc5b 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -819,13 +819,6 @@ static uint64_t scale_tsc(uint64_t host_tsc, uint64_t 
ratio)
     return scaled_host_tsc;
 }
 
-static uint64_t svm_scale_tsc(const struct vcpu *v, uint64_t tsc)
-{
-    ASSERT(cpu_has_tsc_ratio && !v->domain->arch.vtsc);
-
-    return scale_tsc(tsc, hvm_vcpu_tsc_scaling_ratio(v));
-}
-
 static uint64_t svm_get_tsc_offset(uint64_t host_tsc, uint64_t guest_tsc,
     uint64_t ratio)
 {
@@ -2291,7 +2284,6 @@ static struct hvm_function_table __initdata 
svm_function_table = {
 
     .tsc_scaling = {
         .max_ratio = ~TSC_RATIO_RSVD_BITS,
-        .scale_tsc = svm_scale_tsc,
     },
 };
 
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index fda9692..687e39b 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -816,8 +816,7 @@ static void __update_vcpu_system_time(struct vcpu *v, int 
force)
     {
         if ( has_hvm_container_domain(d) && hvm_tsc_scaling_supported )
         {
-            tsc_stamp            =
-                hvm_funcs.tsc_scaling.scale_tsc(v, t->local_tsc_stamp);
+            tsc_stamp            = hvm_scale_tsc(d, 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 6264d9e..fc9616a 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -231,8 +231,6 @@ struct hvm_function_table {
         uint8_t  ratio_frac_bits;
         /* maximum-allowed TSC scaling ratio */
         uint64_t max_ratio;
-
-        uint64_t (*scale_tsc)(const struct vcpu *v, uint64_t tsc);
     } tsc_scaling;
 };
 
@@ -278,6 +276,7 @@ u64 hvm_get_guest_tsc_fixed(struct vcpu *v, u64 at_tsc);
 #define hvm_vcpu_tsc_scaling_ratio(v) \
     ((v)->domain->arch.hvm_domain.tsc_scaling_ratio)
 
+u64 hvm_scale_tsc(const struct domain *d, u64 tsc);
 u64 hvm_get_tsc_scaling_ratio(u32 gtsc_khz);
 
 int hvm_set_mode(struct vcpu *v, int mode);
-- 
2.7.1


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