From mboxrd@z Thu Jan  1 00:00:00 1970
From: Carsten Otte <cotte@de.ibm.com>
Subject: Re: [RFC/PATCH 14/15] guest: detect when running on kvm
Date: Thu, 20 Mar 2008 18:27:53 +0100
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	<20080320101602.f2737c94.randy.dunlap@oracle.com>
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Cc: Christian Ehrhardt <EHRHARDT@de.ibm.com>, hollisb@us.ibm.com,
	arnd@arndb.de, kvm-devel@lists.sourceforge.net,
	mschwid2@linux.vnet.ibm.com, heicars2@linux.vnet.ibm.com,
	jeroney@us.ibm.com, Avi Kivity <avi@qumranet.com>,
	virtualization@lists.linux-foundation.org,
	borntrae@linux.vnet.ibm.com, rvdheij@gmail.com,
	Olaf Schnapper <os@de.ibm.com>, jblunck@suse.de,
	"Zhang,  Xiantao" <xiantao.zhang@intel.com>
To: Randy Dunlap <randy.dunlap@oracle.com>
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Randy Dunlap wrote:
>> Index: kvm/arch/s390/kernel/early.c
>> ===================================================================
>> --- kvm.orig/arch/s390/kernel/early.c
>> +++ kvm/arch/s390/kernel/early.c
>> @@ -143,6 +143,10 @@ static noinline __init void detect_machi
>>  	/* Running on a P/390 ? */
>>  	if (cpuinfo->cpu_id.machine == 0x7490)
>>  		machine_flags |= 4;
>> +
>> +	/* Running under KVM ? */
>> +	if (cpuinfo->cpu_id.version == 0xfe)
> 
> Hi,
> 
> Where are these magic numbers documented?  (0x7490, 0xfe, etc.)
> 
> 
>> +		machine_flags |= 64;
>>  }
>>  
>>  #ifdef CONFIG_64BIT
The cpuid (and most other things about s390 arch) are documented in 
the principles of operation:
http://publibz.boulder.ibm.com/epubs/pdf/a2278324.pdf
http://publibz.boulder.ibm.com/epubs/pdf/dz9zs001.pdf

(see chapter "control instructions" - store cpu id)

The 0xfe however is convention, the kvm arch code sets this value 
where it implements that instruction. See "privileged instructions" patch.

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