x86: Make tsc=reliable override boot time stability checks (d3b8f889) · Commits · 戴 / test

This patch makes the tsc=reliable option disable the boot time stability checks. Currently the option only disables the runtime watchdog checks. This change allows folks who want to override the boot time TSC stability checks and use the TSC when the system would otherwise disqualify it. There still are some situations that the TSC will be disqualified, such as cpufreq scaling. But these are situations where the box will hang if allowed. Patch also includes a fix for an issue found by Thomas Gleixner, where the TSC disqualification message wouldn't be printed after a call to unsynchronized_tsc(). Signed-off-by:

John Stultz <johnstul@us.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: akataria@vmware.com Cc: Stephen Hemminger <shemminger@vyatta.com> LKML-Reference: <1250552447.7212.92.camel@localhost.localdomain> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

Documentation/kernel-parameters.txt

+5 −4

Original line number	Diff line number	Diff line
		@@ -2484,12 +2484,13 @@ and is between 256 and 4096 characters. It is defined in the file
		Format:
		<io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>

		tsc= Disable clocksource-must-verify flag for TSC.
		tsc= Disable clocksource stability checks for TSC.
		Format: <string>
		[x86] reliable: mark tsc clocksource as reliable, this
		disables clocksource verification at runtime.
		Used to enable high-resolution timer mode on older
		hardware, and in virtualized environment.
		disables clocksource verification at runtime, as well
		as the stability checks done at bootup. Used to enable
		high-resolution timer mode on older hardware, and in
		virtualized environment.

		turbografx.map[2\|3]= [HW,JOY]
		TurboGraFX parallel port interface

arch/x86/kernel/tsc.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -825,6 +825,9 @@ __cpuinit int unsynchronized_tsc(void)

		if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
		return 0;

		if (tsc_clocksource_reliable)
		return 0;
		/*
		* Intel systems are normally all synchronized.
		* Exceptions must mark TSC as unstable:
		@@ -832,10 +835,10 @@ __cpuinit int unsynchronized_tsc(void)
		if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
		/* assume multi socket systems are not synchronized: */
		if (num_possible_cpus() > 1)
		tsc_unstable = 1;
		return 1;
		}

		return tsc_unstable;
		return 0;
		}

		static void __init init_tsc_clocksource(void)

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