intel_idle: Handle older CPUs, which stop the TSC in deeper C states, correctly

JIRA: https://issues.redhat.com/browse/RHEL-85522

commit c157d35
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Tue Feb 25 23:37:08 2025 +0100

    intel_idle: Handle older CPUs, which stop the TSC in deeper C states, correctly

    The Intel idle driver is preferred over the ACPI processor idle driver,
    but fails to implement the work around for Core2 generation CPUs, where
    the TSC stops in C2 and deeper C-states. This causes stalls and boot
    delays, when the clocksource watchdog does not catch the unstable TSC
    before the CPU goes deep idle for the first time.

    The ACPI driver marks the TSC unstable when it detects that the CPU
    supports C2 or deeper and the CPU does not have a non-stop TSC.

    Add the equivivalent work around to the Intel idle driver to cure that.

    Fixes: 1873495 ("intel_idle: Use ACPI _CST for processor models without C-state tables")
    Reported-by: Fab Stz <fabstz-it@yahoo.fr>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Fab Stz <fabstz-it@yahoo.fr>
    Cc: All applicable <stable@vger.kernel.org>
    Closes: https://lore.kernel.org/all/10cf96aa-1276-4bd4-8966-c890377030c3@yahoo.fr
    Link: https://patch.msgid.link/87bjupfy7f.ffs@tglx
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Signed-off-by: David Arcari <darcari@redhat.com>

Author: darcari

drivers/idle/intel_idle.c

@@ -55,6 +55,7 @@
 #include <asm/intel-family.h>
 #include <asm/mwait.h>
 #include <asm/spec-ctrl.h>
+#include <asm/tsc.h>
 #include <asm/fpu/api.h>
 #include <asm/smp.h>
 
@@ -1809,6 +1810,9 @@ static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
 		if (intel_idle_state_needs_timer_stop(state))
 			state->flags |= CPUIDLE_FLAG_TIMER_STOP;
 
+		if (cx->type > ACPI_STATE_C1 && !boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
+			mark_tsc_unstable("TSC halts in idle");
+
 		state->enter = intel_idle;
 		state->enter_dead = intel_idle_enter_dead;
 		state->enter_s2idle = intel_idle_s2idle;