linux-kernel - Re: [Xen-devel] Re: [GIT PULL] xen /proc/mtrr implementation

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Date:	Mon, 25 May 2009 10:42:05 +0200
From:	Tomasz Chmielewski <mangoo@...g.org>
To:	LKML <linux-kernel@...r.kernel.org>
CC:	mingo@...e.hu, Alan <alan@...rguk.ukuu.org.uk>,
	Gerd Hoffmann <kraxel@...hat.com>, jeremy@...p.org,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>, JBeulich@...ell.com,
	jbarnes@...tuousgeek.org
Subject: Re: [Xen-devel] Re: [GIT PULL] xen /proc/mtrr implementation

Ingo Molnar wrote:

>>>> Oops, the third "proper technical solutions" is missing.
>>>
>>> Yeah, the third one is to not touch MTRRs after bootup and use PAT.
>>
>> Works only in case the CPU has PAT support.
> 
> Which specific CPU without PAT support do you worry about?

Are these ones (below) good CPU to worry about? That's slightly 
off-topic as they are KVM guests, but still, the guest kernel seems to 
disable PAT (unless I'm mistaken).



KVM-86 + 2.6.27.19 guest:

# dmesg
Initializing cgroup subsys cpuset
Linux version 2.6.27.19-server-1mnb (qateam@...an.mandriva.com) (gcc 
version 4.3.2 (GCC) ) #1 SMP Thu Mar 5 00:09:04 EST 2009
PAT WC disabled due to known CPU erratum.
(...)

# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 2
model name      : QEMU Virtual CPU version 0.10.50
stepping        : 3
cpu MHz         : 2133.285
cache size      : 2048 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu de pse tsc msr pae mce cx8 apic mtrr pge mca cmov 
pat pse36 clflush mmx fxsr sse sse2 syscall lm up pni
bogomips        : 4266.57
clflush size    : 64
power management:


KVM-85 + 2.6.29.1 guest:

# dmesg
Initializing cgroup subsys cpuset
Initializing cgroup subsys cpu
Linux version 2.6.29.1-server-4mnb (herton@...mandriva.com) (gcc version 
4.3.2 (GCC) ) #1 SMP Mon Apr 20 20:10:24 EDT 2009
KERNEL supported cpus:
   Intel GenuineIntel
   AMD AuthenticAMD
   NSC Geode by NSC
   Cyrix CyrixInstead
   Centaur CentaurHauls
   Transmeta GenuineTMx86
   Transmeta TransmetaCPU
   UMC UMC UMC UMC
PAT WC disabled due to known CPU erratum.
(...)

# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 2
model name      : QEMU Virtual CPU version 0.10.0
stepping        : 3
cpu MHz         : 2128.004
cache size      : 2048 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu de pse tsc msr pae mce cx8 apic mtrr pge mca cmov 
pat pse36 clflush mmx fxsr sse sse2 syscall nx lm up pni hypervisor
bogomips        : 4256.00
clflush size    : 64
power management:



-- 
Tomasz Chmielewski
http://wpkg.org

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