[PATCH v6 1/5] x86/hvm: Setup TSC scaling ratio

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

This patch adds a field tsc_scaling_ratio in struct hvm_domain to record
the per-domain TSC scaling ratio, and sets it in tsc_set_info().

Before setting the per-domain TSC scaling ratio, 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>
---
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Boris Ostrovsky <boris.ostrovsky@oracle.com>
CC: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
CC: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
CC: Kevin Tian <kevin.tian@intel.com>
---
Changes in v6:
 For inline assembly in hvm_get_tsc_scaling_ratio():
 * Add a check before inline assembly to avoid #DE from divq.
 * Replace salq by shlq.
 * Split inputs and outputs for dummy and ratio.
 * Turn to named arguments.
 * Put assembly and 'asm (' in the same line.
 Misc:
 * Rename macro hvm_vcpu_tsc_scaling_ratio() into hvm_tsc_scaling_ratio()
   and change its argument type to struct domain *.
---
 xen/arch/x86/hvm/hvm.c            | 38 ++++++++++++++++++++++++++++++++++++++
 xen/arch/x86/hvm/svm/svm.c        |  4 ++--
 xen/arch/x86/time.c               | 10 ++++++++--
 xen/include/asm-x86/hvm/domain.h  |  2 ++
 xen/include/asm-x86/hvm/hvm.h     |  8 ++++++++
 xen/include/asm-x86/hvm/svm/svm.h |  3 ---
 6 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index f46d53c..6c32e99 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -298,6 +298,41 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
     return 1;
 }
 
+/*
+ * Get the ratio to scale host TSC frequency to gtsc_khz. zero will be
+ * returned if TSC scaling is unavailable or ratio cannot be handled
+ * by host CPU. Otherwise, a non-zero ratio will be returned.
+ */
+u64 hvm_get_tsc_scaling_ratio(u32 gtsc_khz)
+{
+    u8 ratio_frac_bits = hvm_funcs.tsc_scaling.ratio_frac_bits;
+    u64 max_ratio = hvm_funcs.tsc_scaling.max_ratio;
+    u64 ratio, dummy;
+
+    if ( !hvm_tsc_scaling_supported )
+        return 0;
+
+    /*
+     * Return early if the quotient is too large to fit in the integral
+     * part of TSC scaling ratio. This also avoids #DE from the following
+     * divq when the quotient can not fit in a 64-bit integer.
+     */
+    if ( gtsc_khz / cpu_khz > (max_ratio >> ratio_frac_bits) )
+        return 0;
+
+    /* ratio = (gtsc_khz << hvm_funcs.tsc_scaling.ratio_frac_bits) / cpu_khz */
+    asm ( "shldq %[frac],%[gkhz],%[zero] ; "
+          "shlq  %[frac],%[gkhz]         ; "
+          "divq  %[hkhz]                   "
+          : "=d" (dummy), "=a" (ratio)
+          : [frac] "c" (ratio_frac_bits),
+            [gkhz] "a" ((u64) gtsc_khz),
+            [zero] "d" (0ULL),
+            [hkhz] "rm" ((u64) cpu_khz) );
+
+    return ratio > max_ratio ? 0 : ratio;
+}
+
 void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
 {
     uint64_t tsc;
@@ -1641,6 +1676,9 @@ int hvm_domain_initialise(struct domain *d)
     register_portio_handler(d, 0xe9, 1, hvm_print_line);
     register_portio_handler(d, 0xcf8, 4, hvm_access_cf8);
 
+    if ( hvm_tsc_scaling_supported )
+        d->arch.hvm_domain.tsc_scaling_ratio = hvm_default_tsc_scaling_ratio;
+
     rc = hvm_funcs.domain_initialise(d);
     if ( rc != 0 )
         goto fail2;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index b22d4a1..7172f25 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -823,7 +823,7 @@ 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, vcpu_tsc_ratio(v));
+    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,
@@ -1000,7 +1000,7 @@ 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, hvm_tsc_scaling_ratio(v->domain));
 }
 
 static void svm_ctxt_switch_from(struct vcpu *v)
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 2248dfa..fda9692 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1865,7 +1865,8 @@ 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 || hvm_tsc_scaling_supported :
+              (d->arch.tsc_khz == cpu_khz ||
+               hvm_get_tsc_scaling_ratio(d->arch.tsc_khz)) :
               incarnation == 0) )
         {
     case TSC_MODE_NEVER_EMULATE:
@@ -1879,7 +1880,8 @@ 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) &&
-                             hvm_tsc_scaling_supported && !d->arch.vtsc;
+                             !d->arch.vtsc &&
+                             hvm_get_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);
@@ -1897,6 +1899,10 @@ void tsc_set_info(struct domain *d,
     d->arch.incarnation = incarnation + 1;
     if ( has_hvm_container_domain(d) )
     {
+        if ( hvm_tsc_scaling_supported && !d->arch.vtsc )
+            d->arch.hvm_domain.tsc_scaling_ratio =
+                hvm_get_tsc_scaling_ratio(d->arch.tsc_khz);
+
         hvm_set_rdtsc_exiting(d, d->arch.vtsc);
         if ( d->vcpu && d->vcpu[0] && incarnation == 0 )
         {
diff --git a/xen/include/asm-x86/hvm/domain.h b/xen/include/asm-x86/hvm/domain.h
index 2446586..4406be9 100644
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -143,6 +143,8 @@ struct hvm_domain {
      */
     uint64_t sync_tsc;
 
+    uint64_t tsc_scaling_ratio;
+
     unsigned long *io_bitmap;
 
     /* List of permanently write-mapped pages. */
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 82d0f9d..ddb1e33 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -272,6 +272,14 @@ u64 hvm_get_guest_tsc_fixed(struct vcpu *v, u64 at_tsc);
 #define hvm_tsc_scaling_supported \
     (!!hvm_funcs.tsc_scaling.ratio_frac_bits)
 
+#define hvm_default_tsc_scaling_ratio \
+    (1ULL << hvm_funcs.tsc_scaling.ratio_frac_bits)
+
+#define hvm_tsc_scaling_ratio(d) \
+    ((d)->arch.hvm_domain.tsc_scaling_ratio)
+
+u64 hvm_get_tsc_scaling_ratio(u32 gtsc_khz);
+
 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);
-- 
2.7.2


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