As noted by Gleb, not advertising SSE2 support implies
no RDTSC barriers.
Signed-off-by: Marcelo Tosatti <[email protected]>
Index: vsyscall/arch/x86/include/asm/pvclock.h
===================================================================
--- vsyscall.orig/arch/x86/include/asm/pvclock.h
+++ vsyscall/arch/x86/include/asm/pvclock.h
@@ -74,6 +74,12 @@ unsigned __pvclock_read_cycles(const str
u8 ret_flags;
version = src->version;
+ /* Note: emulated platforms which do not advertise SSE2 support
+ * result in kvmclock not using the necessary RDTSC barriers.
+ * Without barriers, it is possible that RDTSC instruction reads from
+ * the time stamp counter outside rdtsc_barrier protected section
+ * below, resulting in violation of monotonicity.
+ */
rdtsc_barrier();
offset = pvclock_get_nsec_offset(src);
ret = src->system_time + offset;
--
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