On Thu, Apr 23, 2015 at 3:31 PM, H. Peter Anvin <h...@zytor.com> wrote: > On 04/23/2015 03:29 PM, Andy Lutomirski wrote: >>> >>> Yes, the NULL SS is a special thing in 64-bit mode. I agree that >>> context-switching it is probably the way to go; it should be cheap >>> enough. We might even be able to conditionalize it on an X86_BUG_ flag. >> >> I still don't see why context switches are a better place than just >> before sysret, but I could be convinced. >> > > Because there are way more sysrets than context switches, and Linux is > particularly sensitive to system call latency, by design.
I mean sysret but only when SS might be zero. Denys' approach apparently needs ~4 cycles to check that (not bad), we could (yuck) set a ti flag on context switch. But yes, maybe you're right. --Andy -- 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/
