From mboxrd@z Thu Jan  1 00:00:00 1970
From: Haozhong Zhang <haozhong.zhang@intel.com>
Subject: [PATCH 01/13] x86/time.c: Use system time to calculate
	elapsed_nsec in tsc_get_info()
Date: Mon, 28 Sep 2015 15:13:46 +0800
Message-ID: <1443424438-13404-2-git-send-email-haozhong.zhang@intel.com>
References: <1443424438-13404-1-git-send-email-haozhong.zhang@intel.com>
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Cc: Haozhong Zhang <haozhong.zhang@intel.com>, Kevin Tian <kevin.tian@intel.com>, Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Jun Nakajima <jun.nakajima@intel.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Jan Beulich <jbeulich@suse.com>, Keir Fraser <keir@xen.org>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
List-Id: xen-devel@lists.xenproject.org

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@intel.com>
---
 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