Date: Wed, 22 Oct 2008 12:41:19 -0400 From: Jung-uk Kim <jkim@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r184146 - in head/sys: amd64/amd64 amd64/include i386/i386 i386/include Message-ID: <200810221241.22455.jkim@FreeBSD.org> In-Reply-To: <200810221202.40803.jhb@freebsd.org> References: <200810220001.m9M01rLq011948@svn.freebsd.org> <200810221141.52036.jkim@FreeBSD.org> <200810221202.40803.jhb@freebsd.org>
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On Wednesday 22 October 2008 12:02 pm, John Baldwin wrote: > On Wednesday 22 October 2008 11:41:36 am Jung-uk Kim wrote: > > On Wednesday 22 October 2008 11:01 am, John Baldwin wrote: > > > On Tuesday 21 October 2008 08:01:53 pm Jung-uk Kim wrote: > > > > Author: jkim > > > > Date: Wed Oct 22 00:01:53 2008 > > > > New Revision: 184146 > > > > URL: http://svn.freebsd.org/changeset/base/184146 > > > > > > > > Log: > > > > Set kern.timecounter.invariant_tsc to 1 for AMD CPU family > > > > 10h and higher even if BIOS does not advertise it. > > > > > > > > Modified: > > > > head/sys/amd64/amd64/identcpu.c > > > > head/sys/amd64/include/specialreg.h > > > > head/sys/i386/i386/identcpu.c > > > > head/sys/i386/include/specialreg.h > > > > > > > > Modified: head/sys/amd64/amd64/identcpu.c > > > > > > =============================================================== > > >==== =========== > > > > > > > --- head/sys/amd64/amd64/identcpu.c Tue Oct 21 23:36:28 > > > > 2008 (r184145) +++ head/sys/amd64/amd64/identcpu.c Wed Oct 22 > > > > 00:01:53 2008 (r184146) @@ -348,7 +348,9 @@ > > > > printcpuinfo(void) cpu_feature &= ~CPUID_HTT; > > > > > > > > if (!tsc_is_invariant && > > > > - (amd_pminfo & AMDPM_TSC_INVARIANT)) { > > > > + (strcmp(cpu_vendor, "AuthenticAMD") == 0 && > > > > + ((amd_pminfo & AMDPM_TSC_INVARIANT) != 0 || > > > > + AMD64_CPU_FAMILY(cpu_id) >= 0x10))) { > > > > tsc_is_invariant = 1; > > > > printf("\n P-state invariant TSC"); > > > > } > > > > > > Perhaps a simpler approach might be to just set > > > AMDPM_TSC_INVARIANT for AMD64_CPU_FAMILY(cpu_id) >= 0x10? > > > > It seems Athlon X2 (Family 0Fh, Model 6Bh, Stepping G2) that I > > bought also has invariant TSC although it is not advertised by > > CPUID. If BIOS manufacturer decide to set the bit later, it > > should be honored IMO. > > Err, yeah, my suggestion is something like this: > > /* > * These CPUs have an invariant TSC even though they don't > * always advertise it. > */ > if (strcmp(cpu_vendor, "AuthenticAMD") == 0 && > AMD64_CPU_FAMILY(cpu_id) >= 0x10) > amd_pminfo |= AMDPM_TSC_INVARIANT; > > if (!tsc_is_invariant && > (amd_pminfo & AMDPM_TSC_INVARIANT)) { > tsc_is_invariant; > printf(...); > } > > That will still support any other CPUs that grow the CPUID flag at > some point, it just fakes the CPUID flag for CPUs that we know have > it but just aren't advertising it. Hmm, interesting idea. But please read this: http://docs.freebsd.org/cgi/mid.cgi?200810211605.46927.jkim If Linux people are actually correct, then: if (amd_pminfo & AMDPM_TSC_INVARIANT) smp_tsc = 1; I like to use it later if it is really true. Besides, I hate to set/clear CPUIDs like this. For that, I believe we should have a single feature flag for all amd64/i386 CPUs regardless of vendors, e.g., CPU_CAP_LONGMODE, CPU_CAP_SSE3, CPU_CAP_INVARIANT_TSC, etc. and we should leave the feature variables as is. Jung-uk Kim
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