[Xen-devel] [PATCH v5 1/6] x86/hvm: Collect information of TSC scaling ratio

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

Both VMX TSC scaling and SVM TSC ratio use the 64-bit TSC scaling ratio,
but the number of fractional bits of the ratio is different between VMX
and SVM. This patch adds the architecture code to collect the number of
fractional bits and other related information into fields of struct
hvm_function_table so that they can be used in the common code.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
Changes in v5:
 * Drop "Reviewed-by" from Kevin Tian and Boris Ostrovsky because
   v4 and v5 are changed quite a lot.
 * Put all TSC scaling parameters and callbacks in a sub-structure 
   tsc_scaling in hvm_function_table.
 * Remove the redundant TSC scaling parameter for default TSC scaling
   ratio, which can be derived from the number of fractional bits of
   TSC scaling ratio.
 * Initialize all TSC scaling parameters and callbacks statically,
   except ratio_frac_bits that is initialized to a non-zero value
   if TSC scaling is available.
---
 xen/arch/x86/hvm/hvm.c        |  9 ++++-----
 xen/arch/x86/hvm/svm/svm.c    |  8 +++++++-
 xen/arch/x86/time.c           | 12 ++++++------
 xen/include/asm-x86/hvm/hvm.h | 16 +++++++++++++++-
 4 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index fe382ce..a72a6e7 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -60,7 +60,6 @@
 #include <asm/hvm/nestedhvm.h>
 #include <asm/hvm/event.h>
 #include <asm/hvm/vmx/vmx.h>
-#include <asm/hvm/svm/svm.h> /* for cpu_has_tsc_ratio */
 #include <asm/altp2m.h>
 #include <asm/mtrr.h>
 #include <asm/apic.h>
@@ -312,8 +311,8 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, 
u64 at_tsc)
     else
     {
         tsc = at_tsc ?: rdtsc();
-        if ( cpu_has_tsc_ratio )
-            tsc = hvm_funcs.scale_tsc(v, tsc);
+        if ( hvm_tsc_scaling_supported )
+            tsc = hvm_funcs.tsc_scaling.scale_tsc(v, tsc);
     }
 
     delta_tsc = guest_tsc - tsc;
@@ -344,8 +343,8 @@ u64 hvm_get_guest_tsc_fixed(struct vcpu *v, uint64_t at_tsc)
     else
     {
         tsc = at_tsc ?: rdtsc();
-        if ( cpu_has_tsc_ratio )
-            tsc = hvm_funcs.scale_tsc(v, tsc);
+        if ( hvm_tsc_scaling_supported )
+            tsc = hvm_funcs.tsc_scaling.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 e62dfa1..b22d4a1 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1465,6 +1465,9 @@ const struct hvm_function_table * __init start_svm(void)
     if ( !cpu_has_svm_nrips )
         clear_bit(SVM_FEATURE_DECODEASSISTS, &svm_feature_flags);
 
+    if ( cpu_has_tsc_ratio )
+        svm_function_table.tsc_scaling.ratio_frac_bits = 32;
+
 #define P(p,s) if ( p ) { printk(" - %s\n", s); printed = 1; }
     P(cpu_has_svm_npt, "Nested Page Tables (NPT)");
     P(cpu_has_svm_lbrv, "Last Branch Record (LBR) Virtualisation");
@@ -2286,7 +2289,10 @@ 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,
+    .tsc_scaling = {
+        .max_ratio = ~TSC_RATIO_RSVD_BITS,
+        .scale_tsc = svm_scale_tsc,
+    },
 };
 
 void svm_vmexit_handler(struct cpu_user_regs *regs)
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 5819b9f..2248dfa 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -37,7 +37,6 @@
 #include <asm/hpet.h>
 #include <io_ports.h>
 #include <asm/setup.h> /* for early_time_init */
-#include <asm/hvm/svm/svm.h> /* for cpu_has_tsc_ratio */
 #include <public/arch-x86/cpuid.h>
 
 /* opt_clocksource: Force clocksource to one of: pit, hpet, acpi. */
@@ -815,9 +814,10 @@ static void __update_vcpu_system_time(struct vcpu *v, int 
force)
     }
     else
     {
-        if ( has_hvm_container_domain(d) && cpu_has_tsc_ratio )
+        if ( has_hvm_container_domain(d) && hvm_tsc_scaling_supported )
         {
-            tsc_stamp            = hvm_funcs.scale_tsc(v, t->local_tsc_stamp);
+            tsc_stamp            =
+                hvm_funcs.tsc_scaling.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;
         }
@@ -1758,7 +1758,7 @@ void tsc_get_info(struct domain *d, uint32_t *tsc_mode,
                   uint32_t *incarnation)
 {
     bool_t enable_tsc_scaling = has_hvm_container_domain(d) &&
-                                cpu_has_tsc_ratio && !d->arch.vtsc;
+                                hvm_tsc_scaling_supported && !d->arch.vtsc;
 
     *incarnation = d->arch.incarnation;
     *tsc_mode = d->arch.tsc_mode;
@@ -1865,7 +1865,7 @@ void tsc_set_info(struct domain *d,
          */
         if ( tsc_mode == TSC_MODE_DEFAULT && host_tsc_is_safe() &&
              (has_hvm_container_domain(d) ?
-              d->arch.tsc_khz == cpu_khz || cpu_has_tsc_ratio :
+              d->arch.tsc_khz == cpu_khz || hvm_tsc_scaling_supported :
               incarnation == 0) )
         {
     case TSC_MODE_NEVER_EMULATE:
@@ -1879,7 +1879,7 @@ void tsc_set_info(struct domain *d,
         d->arch.vtsc = !boot_cpu_has(X86_FEATURE_RDTSCP) ||
                        !host_tsc_is_safe();
         enable_tsc_scaling = has_hvm_container_domain(d) &&
-                             cpu_has_tsc_ratio && !d->arch.vtsc;
+                             hvm_tsc_scaling_supported && !d->arch.vtsc;
         d->arch.tsc_khz = (enable_tsc_scaling && gtsc_khz) ? gtsc_khz : 
cpu_khz;
         set_time_scale(&d->arch.vtsc_to_ns, d->arch.tsc_khz * 1000 );
         d->arch.ns_to_vtsc = scale_reciprocal(d->arch.vtsc_to_ns);
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 0b15616..7e87b10 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -222,7 +222,18 @@ 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)(const struct vcpu *v, uint64_t tsc);
+    /*
+     * Parameters and callbacks for hardware-assisted TSC scaling,
+     * which are valid only when the hardware feature is available.
+     */
+    struct {
+        /* number of bits of the fractional part of TSC scaling ratio */
+        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;
 };
 
 extern struct hvm_function_table hvm_funcs;
@@ -258,6 +269,9 @@ 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)
 
+#define hvm_tsc_scaling_supported \
+    (!!hvm_funcs.tsc_scaling.ratio_frac_bits)
+
 int hvm_set_mode(struct vcpu *v, int mode);
 void hvm_init_guest_time(struct domain *d);
 void hvm_set_guest_time(struct vcpu *v, u64 guest_time);
-- 
2.7.1


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