From: Thomas Gleixner Date: Fri, 23 Jan 2026 23:17:55 +0000 (+0100) Subject: x86/tsc: Handle CLOCK_SOURCE_VALID_FOR_HRES correctly X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=79ccb0693a99e1b91eba95c6bd32a3e02be156ae;p=thirdparty%2Fkernel%2Flinux.git x86/tsc: Handle CLOCK_SOURCE_VALID_FOR_HRES correctly Unconditionally setting the CLOCK_SOURCE_VALID_FOR_HRES for the real TSC clocksource is wrong as there is no guarantee that the early TSC was validated for high resolution mode. Set the flag only when the early TSC was validated as otherwise the clocksource selection might enable high resolution mode with a TSC of unknown quality and possibly no way to back out once it is discovered to be unsuitable. Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260123231521.790598171@kernel.org --- diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index f31046f98a923..9ccd58c29409b 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1200,7 +1200,6 @@ static struct clocksource clocksource_tsc = { .read = read_tsc, .mask = CLOCKSOURCE_MASK(64), .flags = CLOCK_SOURCE_IS_CONTINUOUS | - CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_CAN_INLINE_READ | CLOCK_SOURCE_MUST_VERIFY | CLOCK_SOURCE_VERIFY_PERCPU | @@ -1411,6 +1410,15 @@ out: have_art = true; clocksource_tsc.base = &art_base_clk; } + + /* + * Transfer the valid for high resolution flag if it was set on the + * early TSC already. That guarantees that there is no intermediate + * clocksource selected once the early TSC is unregistered. + */ + if (clocksource_tsc_early.flags & CLOCK_SOURCE_VALID_FOR_HRES) + clocksource_tsc.flags |= CLOCK_SOURCE_VALID_FOR_HRES; + clocksource_register_khz(&clocksource_tsc, tsc_khz); unreg: clocksource_unregister(&clocksource_tsc_early);