[Xen-devel] [PATCH] minor cleanup of code that writes to TSC

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

While working on TSC-handling code, I missed an important
piece of code that writes to TSC because it does it
differently than other pieces of code.  Fix that,
and also cleanup a bit to avoid hardcoded constants
and use wrmsrl instead of wrmsr plus handwritten 64-bit
dismembering code.

Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>

diff -r 72d130772f36 xen/arch/x86/smpboot.c
--- a/xen/arch/x86/smpboot.c    Wed Sep 16 09:30:41 2009 +0100
+++ b/xen/arch/x86/smpboot.c    Mon Sep 21 11:03:24 2009 -0600
@@ -223,7 +223,7 @@ static void __init synchronize_tsc_bp (v
                 * We clear the TSC in the last loop:
                 */
                if (i == NR_LOOPS-1)
-                       write_tsc(0, 0);
+                       write_tsc(0L);
 
                /*
                 * Wait for all APs to leave the synchronization point:
@@ -293,7 +293,7 @@ static void __init synchronize_tsc_ap (v
 
                rdtscll(tsc_values[smp_processor_id()]);
                if (i == NR_LOOPS-1)
-                       write_tsc(0, 0);
+                       write_tsc(0L);
 
                atomic_inc(&tsc_count_stop);
                while (atomic_read(&tsc_count_stop) != num_booting_cpus()) mb();
diff -r 72d130772f36 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c       Wed Sep 16 09:30:41 2009 +0100
+++ b/xen/arch/x86/time.c       Mon Sep 21 11:03:24 2009 -0600
@@ -699,7 +699,7 @@ void cstate_restore_tsc(void)
     struct cpu_time *t = &this_cpu(cpu_time);
     struct time_scale sys_to_tsc = scale_reciprocal(t->tsc_scale);
     s_time_t stime_delta;
-    u64 tsc_delta;
+    u64 new_tsc;
 
     if ( boot_cpu_has(X86_FEATURE_NOSTOP_TSC) )
         return;
@@ -708,9 +708,9 @@ void cstate_restore_tsc(void)
     if ( stime_delta < 0 )
         stime_delta = 0;
 
-    tsc_delta = scale_delta(stime_delta, &sys_to_tsc);
+    new_tsc = t->local_tsc_stamp + scale_delta(stime_delta, &sys_to_tsc);
 
-    wrmsrl(MSR_IA32_TSC, t->local_tsc_stamp + tsc_delta);
+    write_tsc(new_tsc);
 }
 
 /***************************************************************************
@@ -1126,8 +1126,7 @@ static void time_calibration_tsc_rendezv
             atomic_inc(&r->semaphore);
 
             if ( i == 0 )
-                write_tsc((u32)r->master_tsc_stamp,
-                          (u32)(r->master_tsc_stamp >> 32));
+                write_tsc(r->master_tsc_stamp);
 
             while ( atomic_read(&r->semaphore) != (2*total_cpus - 1) )
                 mb();
@@ -1140,8 +1139,7 @@ static void time_calibration_tsc_rendezv
                 mb();
 
             if ( i == 0 )
-                write_tsc((u32)r->master_tsc_stamp,
-                          (u32)(r->master_tsc_stamp >> 32));
+                write_tsc(r->master_tsc_stamp);
 
             atomic_inc(&r->semaphore);
             while ( atomic_read(&r->semaphore) > total_cpus )
diff -r 72d130772f36 xen/include/asm-x86/msr.h
--- a/xen/include/asm-x86/msr.h Wed Sep 16 09:30:41 2009 +0100
+++ b/xen/include/asm-x86/msr.h Mon Sep 21 11:03:24 2009 -0600
@@ -82,7 +82,7 @@ static inline void wrmsrl(unsigned int m
 } while(0)
 #endif
 
-#define write_tsc(val1,val2) wrmsr(0x10, val1, val2)
+#define write_tsc(val) wrmsrl(MSR_IA32_TSC, val)
 
 #define rdpmc(counter,low,high) \
      __asm__ __volatile__("rdpmc" \

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