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DateFri, 8 Feb 2008 12:44:19 +0100
FromAndi Kleen <>
SubjectRe: [PATCH] Use global TLB flushes in MTRR code
> because it's not just an open-coded __tlb_flush_all(), it _disables PGE 
> and keeps it so while the MTRR's are changed on all CPUs_.
Yes and? 

> > Your patch adds __flush_tlb_all() which re-enables the PGE bit in cr4, 
> see asm-x86/tlbflush.h:> >         /* clear PGE */
>         write_cr4(cr4 & ~X86_CR4_PGE);
>         /* write old PGE again and flush TLBs */
>         write_cr4(cr4);
> 
> so we'll keep PGE enabled during the MTRR setting - which changes 
> behavior.

It changes behaviour in some minor ways but I don't think it makes any 
difference. PGE only influences TLB flushes (according to its 
specification) and all the TLB flushes still run with PGE disabled.
-Andi



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