[PATCH v12 2/2] x86/viridian: Add partition time reference counter MSR support

[Paul Durrant <paul.durrant@citrix.com>]

This patch optionally re-instates support for the partition time reference
counter that was previously introduced by commit
e36cd2cdc9674a7a4855d21fb7b3e6e17c4bb33b and reverted by commit
1cd4fab14ce25859efa4a2af13475e6650a5506c. The previous implementation was
non-optional and flawed.

This implementation uses the tsc of vcpu0, which is preserved across
save/restore as part of the architectural state, and then converts that
to a 100ns tick using the domain's tsc_khz.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Keir Fraser <keir@xen.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Christoph Egger <chegger@amazon.de>
---
 docs/man/xl.cfg.pod.5            |    8 +++++++-
 tools/libxl/libxl_dom.c          |    4 ++++
 tools/libxl/libxl_types.idl      |    1 +
 xen/arch/x86/hvm/viridian.c      |   29 ++++++++++++++++++++++++-----
 xen/arch/x86/time.c              |    4 ++--
 xen/include/asm-x86/perfc_defn.h |    1 +
 xen/include/asm-x86/time.h       |    4 ++++
 xen/include/public/hvm/params.h  |    9 ++++++++-
 8 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index 1bc7fbc..8bba21c 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -1157,10 +1157,16 @@ This group incorporates the TSC and APIC frequency MSRs. These
 enlightenments can improve performance of Windows 7 and Windows
 Server 2008 R2 onwards.
 
+=item B<time_ref_count>
+
+This group incorporates Partition Time Reference Counter MSR. This
+enlightenment can improve performance of Windows 8 and Windows
+Server 2012 onwards.
+
 =item B<defaults>
 
 This is a special value that enables the default set of groups, which
-is currently the B<base> and B<freq> groups.
+is currently the B<base>, B<freq> and B<time_ref_count> groups.
 
 =item B<all>
 
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 2c500ca..bd21841 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -225,6 +225,7 @@ static int hvm_set_viridian_features(libxl__gc *gc, uint32_t domid,
         /* Enable defaults */
         libxl_bitmap_set(&enlightenments, LIBXL_VIRIDIAN_ENLIGHTENMENT_BASE);
         libxl_bitmap_set(&enlightenments, LIBXL_VIRIDIAN_ENLIGHTENMENT_FREQ);
+        libxl_bitmap_set(&enlightenments, LIBXL_VIRIDIAN_ENLIGHTENMENT_TIME_REF_COUNT);
     }
 
     libxl_for_each_set_bit(v, info->u.hvm.viridian_enable) {
@@ -258,6 +259,9 @@ static int hvm_set_viridian_features(libxl__gc *gc, uint32_t domid,
             mask |= HVMPV_no_freq;
     }
 
+    if (libxl_bitmap_test(&enlightenments, LIBXL_VIRIDIAN_ENLIGHTENMENT_TIME_REF_COUNT))
+        mask |= HVMPV_time_ref_count;
+
     if (mask != 0 &&
         xc_hvm_param_set(CTX->xch,
                          domid,
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 1614b11..90d152f 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -182,6 +182,7 @@ libxl_vendor_device = Enumeration("vendor_device", [
 libxl_viridian_enlightenment = Enumeration("viridian_enlightenment", [
     (0, "base"),
     (1, "freq"),
+    (2, "time_ref_count"),
     ])
 
 #
diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 28c4479..6726168 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -36,11 +36,11 @@
 #define HvNotifyLongSpinWait    8
 
 /* Viridian CPUID 4000003, Viridian MSR availability. */
-#define CPUID3A_MSR_REF_COUNT   (1 << 1)
-#define CPUID3A_MSR_APIC_ACCESS (1 << 4)
-#define CPUID3A_MSR_HYPERCALL   (1 << 5)
-#define CPUID3A_MSR_VP_INDEX    (1 << 6)
-#define CPUID3A_MSR_FREQ        (1 << 11)
+#define CPUID3A_MSR_TIME_REF_COUNT (1 << 1)
+#define CPUID3A_MSR_APIC_ACCESS    (1 << 4)
+#define CPUID3A_MSR_HYPERCALL      (1 << 5)
+#define CPUID3A_MSR_VP_INDEX       (1 << 6)
+#define CPUID3A_MSR_FREQ           (1 << 11)
 
 /* Viridian CPUID 4000004, Implementation Recommendations. */
 #define CPUID4A_MSR_BASED_APIC  (1 << 3)
@@ -93,6 +93,8 @@ int cpuid_viridian_leaves(unsigned int leaf, unsigned int *eax,
                 CPUID3A_MSR_VP_INDEX);
         if ( !(viridian_feature_mask(d) & HVMPV_no_freq) )
             *eax |= CPUID3A_MSR_FREQ;
+        if ( viridian_feature_mask(d) & HVMPV_time_ref_count )
+            *eax |= CPUID3A_MSR_TIME_REF_COUNT;
         break;
     case 4:
         /* Recommended hypercall usage. */
@@ -344,6 +346,23 @@ int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
         *val = v->arch.hvm_vcpu.viridian.apic_assist.raw;
         break;
 
+    case VIRIDIAN_MSR_TIME_REF_COUNT:
+    {
+        uint64_t tsc;
+        struct time_scale tsc_to_ns;
+
+        if ( !(viridian_feature_mask(d) & HVMPV_time_ref_count) )
+            return 0;
+
+        perfc_incr(mshv_rdmsr_time_ref_count);
+        tsc = hvm_get_guest_tsc(pt_global_vcpu_target(d));
+
+        /* convert tsc to count of 100ns periods */
+        set_time_scale(&tsc_to_ns, d->arch.tsc_khz * 1000ul);
+        *val = scale_delta(tsc, &tsc_to_ns) / 100ul;
+        break;
+    }
+
     default:
         return 0;
     }
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index bd89219..74c01e3 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -121,7 +121,7 @@ static inline u32 mul_frac(u32 multiplicand, u32 multiplier)
  * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
  * yielding a 64-bit result.
  */
-static inline u64 scale_delta(u64 delta, struct time_scale *scale)
+u64 scale_delta(u64 delta, struct time_scale *scale)
 {
     u64 product;
 
@@ -272,7 +272,7 @@ static u64 init_pit_and_calibrate_tsc(void)
     return ((end - start) * (u64)CALIBRATE_FRAC);
 }
 
-static void set_time_scale(struct time_scale *ts, u64 ticks_per_sec)
+void set_time_scale(struct time_scale *ts, u64 ticks_per_sec)
 {
     u64 tps64 = ticks_per_sec;
     u32 tps32;
diff --git a/xen/include/asm-x86/perfc_defn.h b/xen/include/asm-x86/perfc_defn.h
index 7d802cc..170da00 100644
--- a/xen/include/asm-x86/perfc_defn.h
+++ b/xen/include/asm-x86/perfc_defn.h
@@ -120,6 +120,7 @@ PERFCOUNTER(mshv_rdmsr_hc_page,         "MS Hv rdmsr hypercall page")
 PERFCOUNTER(mshv_rdmsr_vp_index,        "MS Hv rdmsr vp index")
 PERFCOUNTER(mshv_rdmsr_tsc_frequency,   "MS Hv rdmsr TSC frequency")
 PERFCOUNTER(mshv_rdmsr_apic_frequency,  "MS Hv rdmsr APIC frequency")
+PERFCOUNTER(mshv_rdmsr_time_ref_count,  "MS Hv rdmsr time ref count")
 PERFCOUNTER(mshv_rdmsr_icr,             "MS Hv rdmsr icr")
 PERFCOUNTER(mshv_rdmsr_tpr,             "MS Hv rdmsr tpr")
 PERFCOUNTER(mshv_rdmsr_apic_assist,     "MS Hv rdmsr APIC assist")
diff --git a/xen/include/asm-x86/time.h b/xen/include/asm-x86/time.h
index 420620e..c4d82f6 100644
--- a/xen/include/asm-x86/time.h
+++ b/xen/include/asm-x86/time.h
@@ -76,4 +76,8 @@ void cpuid_time_leaf(uint32_t sub_idx, uint32_t *eax, uint32_t *ebx,
 
 u64 stime2tsc(s_time_t stime);
 
+struct time_scale;
+void set_time_scale(struct time_scale *ts, u64 ticks_per_sec);
+u64 scale_delta(u64 delta, struct time_scale *scale);
+
 #endif /* __X86_TIME_H__ */
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 68d26fd..3c51072 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -88,7 +88,14 @@
 #define _HVMPV_no_freq 1
 #define HVMPV_no_freq  (1 << _HVMPV_no_freq)
 
-#define HVMPV_feature_mask (HVMPV_base_freq|HVMPV_no_freq)
+/* Enable Partition Time Reference Counter (HV_X64_MSR_TIME_REF_COUNT) */
+#define _HVMPV_time_ref_count 2
+#define HVMPV_time_ref_count  (1 << _HVMPV_time_ref_count)
+
+#define HVMPV_feature_mask \
+	(HVMPV_base_freq | \
+	 HVMPV_no_freq | \
+	 HVMPV_time_ref_count)
 
 #endif
 
-- 
1.7.10.4