* Linus Torvalds <torva...@linux-foundation.org> wrote: > On Mon, Sep 21, 2015 at 1:46 AM, Ingo Molnar <mi...@kernel.org> wrote: > > > > Linus, what's your preference? > > So quite frankly, is there any reason we don't just implement > native_read_msr() as just > > unsigned long long native_read_msr(unsigned int msr) > { > int err; > unsigned long long val; > > val = native_read_msr_safe(msr, &err); > WARN_ON_ONCE(err); > return val; > } > > Note: no inline, no nothing. Just put it in arch/x86/lib/msr.c, and be > done with it. I don't see the downside.
Absolutely! > How many msr reads are <i>so</i> critical that the function call overhead > would > matter? Get rid of the inline version of the _safe() thing too, and put that > thing there too. Only a very low number of them is performance critical (because even hw-accelerated MSR accesses are generally slow so we try to avoid MSR accesses in fast paths as much as possible, via shadowing, etc.) - and in the few cases where we have to access an MSR in a fast path we can do those separately. I'm only worried about the 'default' APIs, i.e. rdmsr() that is used throughout arch/x86/ over a hundred times, not about performance critical code paths that get enough testing and enough attention in general. Thanks, Ingo _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel