x86/asm/tsc/sync: Use rdtsc_ordered() in check_tsc_warp() and drop extra barriers
Using get_cycles was unnecessary: check_tsc_warp() is not called on TSC-less systems. Replace rdtsc_barrier(); get_cycles() with rdtsc_ordered(). While we're at it, make the somewhat more dangerous change of removing barrier_before_rdtsc after RDTSC in the TSC warp check code. This should be okay, though -- the vDSO TSC code doesn't have that barrier, so, if removing the barrier from the warp check would cause us to detect a warp that we otherwise wouldn't detect, then we have a genuine bug. Signed-off-by: NAndy Lutomirski <luto@kernel.org> Signed-off-by: NBorislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang Rui <ray.huang@amd.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Len Brown <lenb@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kvm ML <kvm@vger.kernel.org> Link: http://lkml.kernel.org/r/387c4c3a75f875bcde6cd68cee013273a744f364.1434501121.git.luto@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
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