x86/tsc: Add X86_FEATURE_TSC_KNOWN_FREQ flag (47c95a46) · Commits · 戴 / test

The X86_FEATURE_TSC_RELIABLE flag in Linux kernel implies both reliable (at runtime) and trustable (at calibration). But reliable running and trustable calibration independent of each other. Add a new flag X86_FEATURE_TSC_KNOWN_FREQ, which denotes that the frequency is known (via MSR/CPUID). This flag is only meant to skip the long term calibration on systems which have a known frequency. Add X86_FEATURE_TSC_KNOWN_FREQ to the skip the delayed calibration and leave X86_FEATURE_TSC_RELIABLE in place. After converting the existing users of X86_FEATURE_TSC_RELIABLE to use either both flags or just X86_FEATURE_TSC_KNOWN_FREQ we can seperate the functionality. Suggested-by:

Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Bin Gao <bin.gao@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1479241644-234277-2-git-send-email-bin.gao@linux.intel.com Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/cpufeatures.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -106,6 +106,7 @@
		#define X86_FEATURE_APERFMPERF ( 332+28) / APERFMPERF */
		#define X86_FEATURE_EAGER_FPU ( 332+29) / "eagerfpu" Non lazy FPU restore */
		#define X86_FEATURE_NONSTOP_TSC_S3 ( 332+30) / TSC doesn't stop in S3 state */
		#define X86_FEATURE_TSC_KNOWN_FREQ ( 332+31) / TSC has known frequency */

		/* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
		#define X86_FEATURE_XMM3 ( 432+ 0) / "pni" SSE-3 */

arch/x86/kernel/tsc.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -1283,10 +1283,15 @@ static int __init init_tsc_clocksource(void)
		clocksource_tsc.flags \|= CLOCK_SOURCE_SUSPEND_NONSTOP;

		/*
		* Trust the results of the earlier calibration on systems
		* exporting a reliable TSC.
		* When TSC frequency is known (retrieved via MSR or CPUID), we skip
		* the refined calibration and directly register it as a clocksource.
		*
		* We still keep the TSC_RELIABLE flag here to avoid regressions -
		* it will be removed after all the conversion for other code paths
		* connected to this flag is done.
		*/
		if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
		if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE) \|\|
		boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
		clocksource_register_khz(&clocksource_tsc, tsc_khz);
		return 0;
		}

Admin message