On Mon, Jun 16, 2014 at 2:58 PM, H. Peter Anvin <[email protected]> wrote: >> >> For 64-bit, I want to do this instead: >> >> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/seccomp-fastpath&id=a5ec2d7af2c54b55fc7201fa662138b53fbbda39 >> >> I see no reason why the 64-bit badsys code needs its own code path at >> all. I haven't sent it yet because AFAICT it doesn't fix any bug, and >> the series it's a part of isn't ready. >> >> I'm also contemplating rewriting the 64-bit syscall entry work path in C. >> > > Cute... although it still leaves an extra branch for the badsys. It > might perform better than a cmov, but it might not.
I bet that the branch is faster in most cases -- I'd be somewhat surprised if CPUs can speculate through a cmov, and that value is needed for control flow almost immediately. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
