[Xen-devel] [PATCH v2 03/14] x86/time.c: Use correct guest TSC frequency in tsc_set_info()

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

When TSC_MODE_PVRDTSCP is used for a HVM container and TSC scaling is
available, use the non-zero value of argument gtsc_khz of tsc_set_info()
as the guest TSC frequency rather than using the host TSC
frequency. Otherwise, TSC scaling will not be able get the correct ratio
between the host and guest TSC frequencies.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/time.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index b5223cf..1091e69 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1803,6 +1803,8 @@ void tsc_set_info(struct domain *d,
                   uint32_t tsc_mode, uint64_t elapsed_nsec,
                   uint32_t gtsc_khz, uint32_t incarnation)
 {
+    bool_t enable_tsc_scaling;
+
     if ( is_idle_domain(d) || is_hardware_domain(d) )
     {
         d->arch.vtsc = 0;
@@ -1864,7 +1866,9 @@ void tsc_set_info(struct domain *d,
     case TSC_MODE_PVRDTSCP:
         d->arch.vtsc = !boot_cpu_has(X86_FEATURE_RDTSCP) ||
                        !host_tsc_is_safe();
-        d->arch.tsc_khz = cpu_khz;
+        enable_tsc_scaling = has_hvm_container_domain(d) &&
+                             cpu_has_tsc_ratio && d->arch.vtsc;
+        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);
         if ( d->arch.vtsc )
@@ -1872,7 +1876,10 @@ void tsc_set_info(struct domain *d,
         else {
             /* when using native TSC, offset is nsec relative to power-on
              * of physical machine */
-            d->arch.vtsc_offset = scale_delta(rdtsc(), &d->arch.vtsc_to_ns) -
+            struct time_scale *scale = enable_tsc_scaling ?
+                                       &this_cpu(cpu_time).tsc_scale :
+                                       &d->arch.vtsc_to_ns;
+            d->arch.vtsc_offset = scale_delta(rdtsc(), scale) -
                                   elapsed_nsec;
         }
         break;
-- 
2.6.3


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