On Sat, Jun 13, 2015 at 1:57 AM, Borislav Petkov <b...@suse.de> wrote: > On Fri, Jun 12, 2015 at 04:44:53PM -0700, Andy Lutomirski wrote: >> Now that there is no paravirt TSC, the "native" is inappropriate. >> The fact that rdtsc is not ordered can catch people by surprise, so >> call it rdtsc_unordered(). >> >> Signed-off-by: Andy Lutomirski <l...@kernel.org> > > ... > >> @@ -109,7 +109,16 @@ notrace static inline int >> native_write_msr_safe(unsigned int msr, >> extern int rdmsr_safe_regs(u32 regs[8]); >> extern int wrmsr_safe_regs(u32 regs[8]); >> >> -static __always_inline unsigned long long native_read_tsc(void) >> +/** >> + * rdtsc_unordered() - returns the current TSC without ordering constraints >> + * >> + * rdtsc_unordered() returns the result of RDTSC as a 64-bit integer. The >> + * only ordering constraint it supplies is the ordering implied by >> + * "asm volatile": it will put the RDTSC in the place you expect. The >> + * CPU can and will speculatively execute that RDTSC, though, so the >> + * results can be non-monotonic if compared on different CPUs. >> + */ >> +static __always_inline unsigned long long rdtsc_unordered(void) > > I like the rdtsc_ordered() thing because it wraps the barrier and people > cannot just forget it. But let's call this not rdtsc_unordered() but > simply > > rdtsc() > > The "_unordered" suffix is unnecessary IMO since this function is a > simple wrapper around the hw insn and we do that naming scheme with all > such wrappers.
I could go either way here. rdtsc() is weird because people seem to forget about the barrier. Maybe I'm being unnecessarily paranoid. --Andy > > -- > Regards/Gruss, > Boris. > > ECO tip #101: Trim your mails when you reply. > -- -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
