Date: Thu, 21 Mar 2019 02:52:22 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r345359 - in head/sys/cddl/dev/dtrace: amd64 i386 Message-ID: <201903210252.x2L2qMSP022374@repo.freebsd.org>
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Author: markj Date: Thu Mar 21 02:52:22 2019 New Revision: 345359 URL: https://svnweb.freebsd.org/changeset/base/345359 Log: Don't attempt to measure TSC skew when running as a VM guest. It simply doesn't work in general since VCPUs may migrate between physical cores. The approach used to measure skew also doesn't make much sense in a VM. PR: 218452 MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Modified: head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Modified: head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c ============================================================================== --- head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Thu Mar 21 01:16:37 2019 (r345358) +++ head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Thu Mar 21 02:52:22 2019 (r345359) @@ -319,6 +319,9 @@ dtrace_gethrtime_init(void *arg) int i; #endif + if (vm_guest) + return; + /* The current CPU is the reference one. */ sched_pin(); tsc_skew[curcpu] = 0; Modified: head/sys/cddl/dev/dtrace/i386/dtrace_subr.c ============================================================================== --- head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Thu Mar 21 01:16:37 2019 (r345358) +++ head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Thu Mar 21 02:52:22 2019 (r345359) @@ -321,6 +321,9 @@ dtrace_gethrtime_init(void *arg) int i; #endif + if (vm_guest) + return; + /* The current CPU is the reference one. */ sched_pin(); tsc_skew[curcpu] = 0;
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