[Xen-devel] [PATCH 01/13] x86/time.c: Use system time to calculate elapsed_nsec in tsc_get_info()

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

When the TSC mode of a domain is TSC_MODE_DEFAULT and no TSC emulation
is used, the existing tsc_get_info() calculates elapsed_nsec by scaling
the host TSC with a ratio between guest TSC rate and
nanoseconds. However, the result will be incorrect if the guest TSC rate
differs from the host TSC rate. This patch fixes this problem by using
the system time as elapsed_nsec.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/time.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index bbb7e6c..a345efb 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1868,8 +1868,7 @@ void tsc_get_info(struct domain *d, uint32_t *tsc_mode,
             *gtsc_khz = d->arch.tsc_khz;
             break;
         }
-        tsc = rdtsc();
-        *elapsed_nsec = scale_delta(tsc, &d->arch.vtsc_to_ns);
+        *elapsed_nsec = get_s_time();
         *gtsc_khz = cpu_khz;
         break;
     case TSC_MODE_PVRDTSCP:
-- 
2.4.8


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