RE: Linux 2.6.38.4 : regression due to x86 AMD ARAT feature

From: Ostrovsky, Boris
Date: Sun Apr 24 2011 - 15:44:40 EST


It's an old family fh processor (CPUID 00020F42) that cpu_has_amd_erratum(amd_erratum_400) apparently hasn't picked up. Since all fh processors are affected by this erratum I'll replace "c->x86 >= 0xf" with "c->x86 > 0xf" (and probably fix erratum formula anyway).

-boris
________________________________________
From: Jörg-Volker Peetz [peetz@xxxxxxxxxxxxxxx]
Sent: Sunday, April 24, 2011 2:55 PM
To: Borislav Petkov; Jörg-Volker Peetz; linux-kernel@xxxxxxxxxxxxxxx; Ostrovsky, Boris; Herrmann3, Andreas; Petkov, Borislav
Subject: Re: Linux 2.6.38.4 : regression due to x86 AMD ARAT feature

Borislav Petkov wrote, on 04/24/11 20:20:
> On Sun, Apr 24, 2011 at 10:06:36AM +0200, Jörg-Volker Peetz wrote:
>> With 2.6.38.4 the clock slows down and the affected laptop sometimes, e.g. for
>> the output of "ps axuw" to appear, needs an input from the keyboard or the
>> touchpad. Please find attached the kernel config file and the output of dmesg.
>>
>> Commenting out the the lines
>>
>> if (c->x86 >= 0xf && !cpu_has_amd_erratum(amd_erratum_400))
>> set_cpu_cap(c, X86_FEATURE_ARAT);
>>
>> in arch/x86/kernel/cpu/amd.c makes this laptop work as before with kernel
>> 2.6.38.3. I think these lines came with commit
>> d7b7f0c401303dd7eafcff11752fe74d3b75c766.
>
> Hmm, interesting.
>
> Can you send also /proc/cpuinfo please?
>
> Looks like your CPU is a single core K8 revE or something but we'd need
> the exact family info.
>
> Thanks.
>

Here it comes:


processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 36
model name : AMD Turion(tm) 64 Mobile Technology MT-40
stepping : 2
cpu MHz : 800.000
cache size : 1024 KB
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36
clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt lm 3dnowext 3dnow rep_good
nopl pni lahf_lm
bogomips : 1592.98
TLB size : 1024 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc

This is a nice mobile processor and i thought it was sold quite a lot.
--
Best regards,
Jörg-Volker.


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