[Xen-devel] [PATCH v2 5/6] x86/time: refactor read_platform_stime()

[Joao Martins <joao.m.martins@xxxxxxxxxx>]

To fetch the last read from the clocksource which was used to
calculate system_time. In the case of clocksource=tsc we will
use it to set tsc_timestamp.

Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Changes since v1:
 - Add missing spaces between brackets
 - Move plt_stamp_counter to read_platform_stime()
 - Add signature change in time_calibration_std_rendezvous()
---
 xen/arch/x86/time.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 9cadfcb..123aa42 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -568,16 +568,19 @@ static void plt_overflow(void *unused)
     set_timer(&plt_overflow_timer, NOW() + plt_overflow_period);
 }
 
-static s_time_t read_platform_stime(void)
+static s_time_t read_platform_stime(u64 *stamp)
 {
-    u64 count;
+    u64 plt_stamp_counter, count;
     s_time_t stime;
 
     ASSERT(!local_irq_is_enabled());
 
     spin_lock(&platform_timer_lock);
-    count = plt_stamp64 + ((plt_src.read_counter() - plt_stamp) & plt_mask);
+    plt_stamp_counter = plt_src.read_counter();
+    count = plt_stamp64 + ((plt_stamp_counter - plt_stamp) & plt_mask);
     stime = __read_platform_stime(count);
+    if ( stamp )
+        *stamp = plt_stamp_counter;
     spin_unlock(&platform_timer_lock);
 
     return stime;
@@ -727,7 +730,7 @@ void cstate_restore_tsc(void)
     if ( boot_cpu_has(X86_FEATURE_NONSTOP_TSC) )
         return;
 
-    write_tsc(stime2tsc(read_platform_stime()));
+    write_tsc(stime2tsc(read_platform_stime(NULL)));
 }
 
 /***************************************************************************
@@ -1046,7 +1049,7 @@ int cpu_frequency_change(u64 freq)
 
     local_irq_disable();
     /* Platform time /first/, as we may be delayed by platform_timer_lock. */
-    t->stime_master_stamp = read_platform_stime();
+    t->stime_master_stamp = read_platform_stime(NULL);
     /* TSC-extrapolated time may be bogus after frequency change. */
     /*t->stime_local_stamp = get_s_time();*/
     t->stime_local_stamp = t->stime_master_stamp;
@@ -1364,7 +1367,7 @@ static void time_calibration_tsc_rendezvous(void *_r)
 
             if ( r->master_stime == 0 )
             {
-                r->master_stime = read_platform_stime();
+                r->master_stime = read_platform_stime(NULL);
                 r->master_tsc_stamp = rdtsc();
             }
             atomic_inc(&r->semaphore);
@@ -1409,7 +1412,7 @@ static void time_calibration_std_rendezvous(void *_r)
     {
         while ( atomic_read(&r->semaphore) != (total_cpus - 1) )
             cpu_relax();
-        r->master_stime = read_platform_stime();
+        r->master_stime = read_platform_stime(NULL);
         mb(); /* write r->master_stime /then/ signal */
         atomic_inc(&r->semaphore);
     }
@@ -1456,7 +1459,7 @@ void init_percpu_time(void)
 
     local_irq_save(flags);
     t->local_tsc_stamp = rdtsc();
-    now = read_platform_stime();
+    now = read_platform_stime(NULL);
     local_irq_restore(flags);
 
     t->stime_master_stamp = now;
-- 
2.1.4


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