[Xen-devel] [PATCH 1/2] x86/viridian: Time Reference Count MSR

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

This viridian MSR is a read-only source of time (in units of 100ns) since the
domain started.

From: Paul Durrant <paul.durrant@xxxxxxxxxx>
Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>

---
---
 xen/arch/x86/hvm/viridian.c      |   24 ++++++++++++++++--------
 xen/include/asm-x86/perfc_defn.h |    1 +
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index a6721c3..f363037 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -17,13 +17,14 @@
 #include <public/hvm/hvm_op.h>
 
 /* Viridian MSR numbers. */
-#define VIRIDIAN_MSR_GUEST_OS_ID 0x40000000
-#define VIRIDIAN_MSR_HYPERCALL   0x40000001
-#define VIRIDIAN_MSR_VP_INDEX    0x40000002
-#define VIRIDIAN_MSR_EOI         0x40000070
-#define VIRIDIAN_MSR_ICR         0x40000071
-#define VIRIDIAN_MSR_TPR         0x40000072
-#define VIRIDIAN_MSR_APIC_ASSIST 0x40000073
+#define VIRIDIAN_MSR_GUEST_OS_ID                0x40000000
+#define VIRIDIAN_MSR_HYPERCALL                  0x40000001
+#define VIRIDIAN_MSR_VP_INDEX                   0x40000002
+#define VIRIDIAN_MSR_TIME_REF_COUNT             0x40000020
+#define VIRIDIAN_MSR_EOI                        0x40000070
+#define VIRIDIAN_MSR_ICR                        0x40000071
+#define VIRIDIAN_MSR_TPR                        0x40000072
+#define VIRIDIAN_MSR_APIC_ASSIST                0x40000073
 
 /* Viridian Hypercall Status Codes. */
 #define HV_STATUS_SUCCESS                       0x0000
@@ -33,6 +34,7 @@
 #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)
@@ -83,7 +85,8 @@ int cpuid_viridian_leaves(unsigned int leaf, unsigned int 
*eax,
         break;
     case 3:
         /* Which hypervisor MSRs are available to the guest */
-        *eax = (CPUID3A_MSR_APIC_ACCESS |
+        *eax = (CPUID3A_MSR_REF_COUNT   |
+                CPUID3A_MSR_APIC_ACCESS |
                 CPUID3A_MSR_HYPERCALL   |
                 CPUID3A_MSR_VP_INDEX);
         break;
@@ -305,6 +308,11 @@ int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
         *val = v->vcpu_id;
         break;
 
+    case VIRIDIAN_MSR_TIME_REF_COUNT:
+        perfc_incr(mshv_rdmsr_time_ref_count);
+        *val = hvm_get_guest_time(v) / 100;
+        break;
+
     case VIRIDIAN_MSR_ICR:
         perfc_incr(mshv_rdmsr_icr);
         *val = (((uint64_t)vlapic_get_reg(vcpu_vlapic(v), APIC_ICR2) << 32) |
diff --git a/xen/include/asm-x86/perfc_defn.h b/xen/include/asm-x86/perfc_defn.h
index 5eaa417..bd251f5 100644
--- a/xen/include/asm-x86/perfc_defn.h
+++ b/xen/include/asm-x86/perfc_defn.h
@@ -118,6 +118,7 @@ PERFCOUNTER(mshv_call_long_wait,        "MS Hv Notify long 
wait")
 PERFCOUNTER(mshv_rdmsr_osid,            "MS Hv rdmsr Guest OS ID")
 PERFCOUNTER(mshv_rdmsr_hc_page,         "MS Hv rdmsr hypercall page")
 PERFCOUNTER(mshv_rdmsr_vp_index,        "MS Hv rdmsr vp index")
+PERFCOUNTER(mshv_rdmsr_time_ref_count,  "MS Hv rdmsr time reference 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")
-- 
1.7.10.4


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