[PATCH v3 08/13] x86/hvm: Setup TSC scaling ratio

[Haozhong Zhang <haozhong.zhang@intel.com>]

This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
record the TSC scaling ratio, and sets it up when tsc_set_info() is
called for a vcpu or when a vcpu is restored or reset.

Before applying the TSC scaling ratio to CPU, we check its validity in
tsc_set_info(). If an invalid ratio is given, we will leave the default
value in tsc_scaling_ratio (i.e. ratio = 1) and setup guest TSC as if no
TSC scaling is used:
* For TSC_MODE_FAULT,
  - if a user-specified TSC frequency is given, we will set the guest
    TSC frequency to it; otherwise, we set it to the host TSC frequency.
  - if guest TSC frequency does not equal to host TSC frequency, we will
    emulate guest TSC (i.e. d->arch.vtsc is set to 1). In both cases,
    guest TSC runs in the guest TSC frequency.
* For TSC_MODE_PVRDTSCP,
  - we set the guest TSC frequency to the host TSC frequency.
  - guest rdtsc is executed natively in the host TSC frequency as
    before.
  - if rdtscp is not available to guest, it will be emulated; otherwise,
    it will be executed natively. In both cases, guest rdtscp gets TSC
    in the host TSC frequency as before.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
Changes in v3:
 (addressing Boris Ostrovsky's comments)
 * Remove redundant checks.
 * Update comments in tsc_set_info(): during initial boot -> during domain creation.
 (addressing Kevin Tian's comments)
 * Add a validation step to check TSC scaling ratio before applying it
   to the hardware. If the validation fails, we will fallback to Xen's
   original way to handle guest TSC. hvm_setup_tsc_scaling() is always
   called when the validation succeeds, so it shoud never fail now.

 xen/arch/x86/hvm/hvm.c            | 41 +++++++++++++++++++++++++++++++++++++++
 xen/arch/x86/hvm/svm/svm.c        |  6 ++++--
 xen/arch/x86/time.c               | 19 +++++++++++++++---
 xen/include/asm-x86/hvm/hvm.h     |  6 ++++++
 xen/include/asm-x86/hvm/svm/svm.h |  3 ---
 xen/include/asm-x86/hvm/vcpu.h    |  2 ++
 6 files changed, 69 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 3648a44..3bf99b1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -65,6 +65,7 @@
 #include <asm/mtrr.h>
 #include <asm/apic.h>
 #include <asm/vm_event.h>
+#include <asm/math64.h>
 #include <public/sched.h>
 #include <public/hvm/ioreq.h>
 #include <public/version.h>
@@ -301,6 +302,42 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
     return 1;
 }
 
+bool_t hvm_validate_tsc_scaling_ratio(uint32_t gtsc_khz)
+{
+    u64 ratio;
+
+    if ( !hvm_funcs.tsc_scaling_supported )
+        return FALSE;
+
+    ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+                            gtsc_khz, cpu_khz);
+
+    return (!ratio || ratio > hvm_funcs.max_tsc_scaling_ratio) ? FALSE : TRUE;
+}
+
+void hvm_setup_tsc_scaling(struct vcpu *v)
+{
+    u64 ratio;
+
+    if ( !hvm_funcs.tsc_scaling_supported )
+        return;
+
+    /*
+     * The multiplication of the first two terms may overflow a 64-bit
+     * integer, so use mul_u64_u32_div() instead to keep precision.
+     */
+    ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+                            v->domain->arch.tsc_khz, cpu_khz);
+
+    if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
+        return;
+
+    v->arch.hvm_vcpu.tsc_scaling_ratio = ratio;
+
+    if ( hvm_funcs.setup_tsc_scaling )
+        hvm_funcs.setup_tsc_scaling(v);
+}
+
 void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
 {
     uint64_t tsc;
@@ -2026,6 +2063,8 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
     if ( hvm_funcs.load_cpu_ctxt(v, &ctxt) < 0 )
         return -EINVAL;
 
+    hvm_setup_tsc_scaling(v);
+
     v->arch.hvm_vcpu.msr_tsc_aux = ctxt.msr_tsc_aux;
 
     seg.limit = ctxt.idtr_limit;
@@ -5504,6 +5543,8 @@ void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, uint16_t ip)
     hvm_set_segment_register(v, x86_seg_gdtr, &reg);
     hvm_set_segment_register(v, x86_seg_idtr, &reg);
 
+    hvm_setup_tsc_scaling(v);
+
     /* Sync AP's TSC with BSP's. */
     v->arch.hvm_vcpu.cache_tsc_offset =
         v->domain->vcpu[0]->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 95795ce..b58f1e8 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -811,7 +811,7 @@ static uint64_t svm_scale_tsc(struct vcpu *v, uint64_t tsc)
     if ( !cpu_has_tsc_ratio || d->arch.vtsc )
         return tsc;
 
-    return scale_tsc(tsc, vcpu_tsc_ratio(v));
+    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,
@@ -986,7 +986,7 @@ 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.hvm_vcpu.tsc_scaling_ratio);
 }
 
 static void svm_ctxt_switch_from(struct vcpu *v)
@@ -1193,6 +1193,8 @@ static int svm_vcpu_initialise(struct vcpu *v)
 
     svm_guest_osvw_init(v);
 
+    v->arch.hvm_vcpu.tsc_scaling_ratio = DEFAULT_TSC_RATIO;
+
     return 0;
 }
 
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index b31634a..e69d9de 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1864,7 +1864,8 @@ 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_validate_tsc_scaling_ratio(d->arch.tsc_khz)) :
               incarnation == 0) )
         {
     case TSC_MODE_NEVER_EMULATE:
@@ -1878,7 +1879,8 @@ 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;
+                             !d->arch.vtsc &&
+                             hvm_validate_tsc_scaling_ratio(gtsc_khz ?: cpu_khz);
         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);
@@ -1897,9 +1899,20 @@ void tsc_set_info(struct domain *d,
     if ( has_hvm_container_domain(d) )
     {
         hvm_set_rdtsc_exiting(d, d->arch.vtsc);
-        if ( d->vcpu && d->vcpu[0] && incarnation == 0 )
+        if ( d->vcpu && d->vcpu[0] )
         {
             /*
+             * TSC scaling ratio on BSP is set here during domain
+             * creation, while the same TSC scaling ratio on APs will
+             * be set in hvm_vcpu_reset_state().
+             */
+            if ( !d->arch.vtsc )
+                hvm_setup_tsc_scaling(d->vcpu[0]);
+
+            if ( incarnation )
+                return;
+
+            /*
              * set_tsc_offset() is called from hvm_vcpu_initialise() before
              * tsc_set_info(). New vtsc mode may require recomputing TSC
              * offset.
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 12f9f24..6b49da8 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -226,6 +226,9 @@ struct hvm_function_table {
     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);
 };
 
 extern struct hvm_function_table hvm_funcs;
@@ -261,6 +264,9 @@ 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)
 
+bool_t hvm_validate_tsc_scaling_ratio(uint32_t gtsc_khz);
+void hvm_setup_tsc_scaling(struct vcpu *v);
+
 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);
diff --git a/xen/include/asm-x86/hvm/svm/svm.h b/xen/include/asm-x86/hvm/svm/svm.h
index d60ec23..c954b7e 100644
--- a/xen/include/asm-x86/hvm/svm/svm.h
+++ b/xen/include/asm-x86/hvm/svm/svm.h
@@ -97,9 +97,6 @@ extern u32 svm_feature_flags;
 /* TSC rate */
 #define DEFAULT_TSC_RATIO       0x0000000100000000ULL
 #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);
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 152d9f3..901c988 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -175,6 +175,8 @@ struct hvm_vcpu {
     u64                 msr_tsc_adjust;
     u64                 msr_xss;
 
+    u64                 tsc_scaling_ratio;
+
     union {
         struct arch_vmx_struct vmx;
         struct arch_svm_struct svm;
-- 
2.4.8