From owner-freebsd-hackers@FreeBSD.ORG  Thu Jul 29 16:57:36 2010
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Date: Thu, 29 Jul 2010 19:57:33 +0300
From: Andriy Gapon <avg@icyb.net.ua>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: coherence-problem on the mapped memory buffer
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on 29/07/2010 19:13 Andriy Gapon said the following:
> on 29/07/2010 17:13 Alexander Fiveg said the following:
>> P.S. Details about hardware and used software:
>> 1. /var/run/dmesg.boot :
>> ...
>> CPU: Dual Core AMD Opteron(tm) Processor 865 (1800.01-MHz 686-class CPU)
>>   Origin = "AuthenticAMD"  Id = 0x20f10  Family = f  Model = 21  Stepping = 0
>>   
>> Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
>>   Features2=0x1<SSE3>
>>   AMD Features=0xe2500800<SYSCALL,NX,MMX+,FFXSR,LM,3DNow!+,3DNow!>
>>   AMD Features2=0x3<LAHF,CMP>
>> real memory  = 3758030848 (3583 MB)
>> avail memory = 3677495296 (3507 MB)
>> ACPI APIC Table: <A M I  OEMAPIC >
>> FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
>> FreeBSD/SMP: 4 package(s) x 2 core(s)
>> ...
>>
>> 2. uname -v
>> FreeBSD 9.0-CURRENT #3
>>
>> 3. sysctl kern.osreldate
>> kern.osreldate: 900014
>>
>> 4. //depot/projects/soc2010/ringmap/

In fact I have a suspicion that the problem might have to do with multiple
mappings of the shared pages, but far from sure...
Take a look at Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 3A - System Programming Guide, Part 1; Chapter 11.12.4 Programming the PAT;
starting at the following words:
«The PAT allows any memory type to be specified in the page tables, and therefore
it is possible to have a single physical page mapped to two or more different
linear addresses, each with different memory types. Intel does not support this
practice...»



-- 
Andriy Gapon