[Xen-devel] [PATCH v7 2/5] 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>
Acked-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> for SVM bits
---
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
CC: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
CC: Kevin Tian <kevin.tian@xxxxxxxxx>
---
Mixing named and positional operands is tested with gcc 4.1.2. It can 
be compiled without any errors/warnings and provides the same result at 
runtime as that compiled by newer version of gcc (v4.8.4).

Changes in v7:
 For inline assembly in hvm_scale_tsc():
 * Add '&' to the restriction of output operand 'dummy'.
---
 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 6c32e99..2d87de4 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -333,6 +333,23 @@ u64 hvm_get_tsc_scaling_ratio(u32 gtsc_khz)
     return ratio > 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 %[ratio]; shrdq %[frac],%%rdx,%[tsc]"
+          : [tsc] "+a" (tsc), "=&d" (dummy)
+          : [frac] "c" (hvm_funcs.tsc_scaling.ratio_frac_bits),
+            [ratio] "rm" (ratio) );
+
+    return tsc;
+}
+
 void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
 {
     uint64_t tsc;
@@ -347,7 +364,7 @@ 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;
@@ -379,7 +396,7 @@ 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 7172f25..979d226 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_tsc_scaling_ratio(v->domain));
-}
-
 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 ddb1e33..c5c9328 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_tsc_scaling_ratio(d) \
     ((d)->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);
-- 
2.4.8


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