Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled"

[Paolo Bonzini]

On 11/03/2016 14:40, Borislav Petkov wrote:
> On Fri, Mar 11, 2016 at 01:23:56PM +0000, One Thousand Gnomes wrote:
>> > Pentium Pro has MTRR, PAT came later.
> Yep, this page says so too:
> 
> http://www.cpu-world.com/CPUs/Pentium-II/Intel-Pentium%20Pro%20200%201%20MB%20-%20GJ80521EX200%201M%20%28BP80521200%201M%29.html
> 
>> > I believe the qemu32 CPU isn't a "real" CPU type therefore.
> And why is that so? I suspect it has again something to do with
> migration and fun. Let me add the kvm ML.
> 
> Guys, does anyone have an idea why
> 
> #define PPRO_FEATURES (CPUID_FP87 | CPUID_DE | CPUID_PSE | CPUID_TSC | \
>           CPUID_MSR | CPUID_MCE | CPUID_CX8 | CPUID_PGE | CPUID_CMOV | \
>           CPUID_PAT | CPUID_FXSR | CPUID_MMX | CPUID_SSE | CPUID_SSE2 | \
>           CPUID_PAE | CPUID_SEP | CPUID_APIC)
> 
> has CPUID_PAT *instead* of CPUID_MTRR?

Somebody got it wrong 10-ish years ago, and nobody has ever checked since.

But, don't use qemu32 or qemu64.  Use kvm32 and kvm64, or better
something like the host you run on ("-cpu Nehalem", "-cpu SandyBridge",
"-cpu Haswell-noTSX" etc.).

I really, really should fix those defaults...

Paolo