On Tue, 17 Nov 2015, Borislav Petkov wrote: > On Mon, Nov 16, 2015 at 09:02:15PM -0800, H. Peter Anvin wrote: > > On 11/16/15 13:25, Thomas Gleixner wrote: > > > On Mon, 16 Nov 2015, Borislav Petkov wrote: > > >> -/* > > >> - * disable flag for tsc. Takes effect by clearing the TSC cpu flag > > >> - * in cpu/common.c > > >> - */ > > >> -int __init notsc_setup(char *str) > > >> +/* Disable the TSC feature flag to avoid further TSC use. */ > > >> +int __init notsc_setup(void) > > >> { > > >> +#ifndef CONFIG_X86_TSC > > >> setup_clear_cpu_cap(X86_FEATURE_TSC); > > > > > > This is silly, really. > > > > > > If CONFIG_X86_TSC is disabled then we should just not compile tsc.c at > > > all and map cpu_has_tsc and stuff depending on it to false. > > > > > > > CONFIG_X86_TSC means TSC is obligatory, not that it is supported. > > Hmm, I'd still need to untangle tsc.c though for people who want to > disable it for whatever reason.
There is an interesting problem: tsc_init() { tsc_khz = x86_platform.calibrate_tsc(); if (!tsc_khz) { mark_tsc_unstable("could not calculate TSC khz"); ... } In the current code we do NOT use TSC for sched_clock() and that's correct as we have no idea what the TSC frequency is. With your changes that is not longer the case, so you end up with a completely wreckaged sched clock. Thanks, tglx -- 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/