Date: Wed, 2 Oct 2019 13:43:24 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r353006 - stable/12/sys/x86/x86 Message-ID: <201910021343.x92DhODD060319@repo.freebsd.org>
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Author: kib Date: Wed Oct 2 13:43:24 2019 New Revision: 353006 URL: https://svnweb.freebsd.org/changeset/base/353006 Log: MFC r352684: x86: Fall back to leaf 0x16 if TSC frequency is obtained by CPUID and leaf 0x15 is not functional. Modified: stable/12/sys/x86/x86/tsc.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/x86/x86/tsc.c ============================================================================== --- stable/12/sys/x86/x86/tsc.c Wed Oct 2 13:36:54 2019 (r353005) +++ stable/12/sys/x86/x86/tsc.c Wed Oct 2 13:43:24 2019 (r353006) @@ -133,7 +133,11 @@ tsc_freq_vmware(void) /* * Calculate TSC frequency using information from the CPUID leaf 0x15 - * 'Time Stamp Counter and Nominal Core Crystal Clock'. It should be + * 'Time Stamp Counter and Nominal Core Crystal Clock'. If leaf 0x15 + * is not functional, as it is on Skylake/Kabylake, try 0x16 'Processor + * Frequency Information'. Leaf 0x16 is described in the SDM as + * informational only, but if 0x15 did not work, and TSC calibration + * is disabled, it is the best we can get at all. It should still be * an improvement over the parsing of the CPU model name in * tsc_freq_intel(), when available. */ @@ -145,10 +149,20 @@ tsc_freq_cpuid(void) if (cpu_high < 0x15) return (false); do_cpuid(0x15, regs); - if (regs[0] == 0 || regs[1] == 0 || regs[2] == 0) + if (regs[0] != 0 && regs[1] != 0 && regs[2] != 0) { + tsc_freq = (uint64_t)regs[2] * regs[1] / regs[0]; + return (true); + } + + if (cpu_high < 0x16) return (false); - tsc_freq = (uint64_t)regs[2] * regs[1] / regs[0]; - return (true); + do_cpuid(0x16, regs); + if (regs[0] != 0) { + tsc_freq = (uint64_t)regs[0] * 1000000; + return (true); + } + + return (false); } static void
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