Andi, On Tue, 8 Sep 2015, Andi Kleen wrote: > > Hmm, I didn't mean mfence can't serialize the instructions. For a true > > IO, a serialization can't guarantee device finishes the IO, we generally > > read some safe IO registers to wait IO finish. I completely don't know > > if this case fits here though. > > Sorry for the late answer. We (Intel) analyzed this case in detail and > can confirm that the following sequence > > 1. Memory-mapped write to LVT Timer Register, setting bits 18:17 to 10b. > 23. MFENCE. > 4. WRMSR to the IA32_TSC_DEADLINE MSR the desired deadline. > > has the same effect as the loop algorithm described in the SDM on all Intel > CPUs. So it's fine to use MFENCE here. Thanks for the confirmation. It would have been really surprising if that wouldn't work. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html