[Xen-devel] [PATCH v2 04/14] x86/time.c: Use correct guest TSC frequency in tsc_get_info()

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

When the TSC mode of a HVM container is TSC_MODE_DEFAULT or
TSC_MODE_PVRDTSCP and no TSC emulation is used, the existing
tsc_get_info() uses the host TSC frequency (cpu_khz) as the guest TSC
frequency. However, tsc_set_info() may set the guest TSC frequency to a
value different than the host. In order to keep consistent to
tsc_set_info(), this patch makes tsc_get_info() use the value set by
tsc_set_info() as the guest TSC frequency.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/time.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 1091e69..95df4f1 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1749,6 +1749,9 @@ void tsc_get_info(struct domain *d, uint32_t *tsc_mode,
                   uint64_t *elapsed_nsec, uint32_t *gtsc_khz,
                   uint32_t *incarnation)
 {
+    bool_t enable_tsc_scaling = has_hvm_container_domain(d) &&
+                                cpu_has_tsc_ratio;
+
     *incarnation = d->arch.incarnation;
     *tsc_mode = d->arch.tsc_mode;
 
@@ -1769,7 +1772,7 @@ void tsc_get_info(struct domain *d, uint32_t *tsc_mode,
         }
         tsc = rdtsc();
         *elapsed_nsec = scale_delta(tsc, &d->arch.vtsc_to_ns);
-        *gtsc_khz = cpu_khz;
+        *gtsc_khz = enable_tsc_scaling ? d->arch.tsc_khz : cpu_khz;
         break;
     case TSC_MODE_PVRDTSCP:
         if ( d->arch.vtsc )
@@ -1779,10 +1782,13 @@ void tsc_get_info(struct domain *d, uint32_t *tsc_mode,
         }
         else
         {
+            struct time_scale *scale = enable_tsc_scaling ?
+                                       &this_cpu(cpu_time).tsc_scale :
+                                       &d->arch.vtsc_to_ns;
             tsc = rdtsc();
-            *elapsed_nsec = scale_delta(tsc, &d->arch.vtsc_to_ns) -
+            *elapsed_nsec = scale_delta(tsc, scale) -
                             d->arch.vtsc_offset;
-            *gtsc_khz = 0; /* ignored by tsc_set_info */
+            *gtsc_khz = enable_tsc_scaling ? d->arch.tsc_khz : 0;
         }
         break;
     }
-- 
2.6.3


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