On Thu, 2016-03-10 at 14:04 -0500, Paul Gortmaker wrote: > [Re: runtime regression with "x86/mm/pat: Emulate PAT when it is > disabled"] On 10/03/2016 (Thu 18:20) Borislav Petkov wrote: > > > On Thu, Mar 10, 2016 at 09:49:51AM -0700, Toshi Kani wrote: > > > This confirms the issue - QEMU's virtual Intel CPU does not support > > > MTRR. > > > > > > When MTRR is disabled, the kernel does not call pat_init(). > > > pat_enabled() is still set to true when CONFIG_X86_PAT is set. > > > CONFIG_X86_PAT depends on CONFIG_MTRR, and assumes that MTRR is > > > enabled. > > > > Aha, so "qemu32" model doesn't support MTRRs but "kvm32" does, for > > example. And so do the majority of the other CPU types. > > So, I guess that is a qemu bug? If there is no real silicon out there > that has no MTRR but does claim PAT, then qemu32 is a flawed CPU type?
It turns out that your qemu's virtual CPU does not support PAT, either. :-) So, it is consistent on this regard. I will send patches to address this issue. Thanks, -Toshi
