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-rw-r--r--arch/x86/kernel/vsyscall_64.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 0b8b6690a86d..44153afc9067 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -17,6 +17,9 @@
* want per guest time just set the kernel.vsyscall64 sysctl to 0.
*/
+/* Disable profiling for userspace code: */
+#define DISABLE_BRANCH_PROFILING
+
#include <linux/time.h>
#include <linux/init.h>
#include <linux/kernel.h>
@@ -128,7 +131,16 @@ static __always_inline void do_vgettimeofday(struct timeval * tv)
gettimeofday(tv,NULL);
return;
}
+
+ /*
+ * Surround the RDTSC by barriers, to make sure it's not
+ * speculated to outside the seqlock critical section and
+ * does not cause time warps:
+ */
+ rdtsc_barrier();
now = vread();
+ rdtsc_barrier();
+
base = __vsyscall_gtod_data.clock.cycle_last;
mask = __vsyscall_gtod_data.clock.mask;
mult = __vsyscall_gtod_data.clock.mult;
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