x86: No need for disable_tsc_sync when full 64-bit TSC cannot be written

During boot we only write zero to the TSCs, which is safe.

Signed-off-by: Keir Fraser <keir@xen.org>

3 files changed, 0 insertions, 17 deletions

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 35f3c153b7..b0b9f52d65 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -172,12 +172,6 @@ valid_k7:
  * then we print a warning if not, and always resync.
  */
 
-/*
- * TSC's upper 32 bits can't be written in earlier CPUs (before
- * Prescott), there is no way to resync one AP against BP.
- */
-bool_t disable_tsc_sync;
-
 static atomic_t tsc_start_flag = ATOMIC_INIT(0);
 static atomic_t tsc_count_start = ATOMIC_INIT(0);
 static atomic_t tsc_count_stop = ATOMIC_INIT(0);
@@ -194,9 +188,6 @@ static void __init synchronize_tsc_bp (void)
 	unsigned int one_usec;
 	int buggy = 0;
 
-	if ( disable_tsc_sync )
-		return;
-
 	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
 		printk("TSC is reliable, synchronization unnecessary\n");
 		return;
@@ -294,9 +285,6 @@ static void __init synchronize_tsc_ap (void)
 {
 	int i;
 
-	if ( disable_tsc_sync )
-		return;
-
 	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
 		return;
 
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 6451dd3f8b..c08f815b17 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1473,9 +1473,6 @@ static void __init tsc_check_writability(void)
     /* cstate_restore_tsc() must not be used (or do nothing) */
     if ( !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) )
         cpuidle_disable_deep_cstate();
-
-    /* synchronize_tsc_slave() must do nothing */
-    disable_tsc_sync = 1;
 }
 
 /* Late init function (after all CPUs are booted). */
diff --git a/xen/include/asm-x86/time.h b/xen/include/asm-x86/time.h
index 6e9410aedd..724fc4a93c 100644
--- a/xen/include/asm-x86/time.h
+++ b/xen/include/asm-x86/time.h
@@ -27,8 +27,6 @@ void calibrate_tsc_ap(void);
 
 typedef u64 cycles_t;
 
-extern bool_t disable_tsc_sync;
-
 static inline cycles_t get_cycles(void)
 {
     cycles_t c;