Messages in this thread | | | Date | Fri, 4 May 2018 14:12:44 -0700 | From | Matthew Wilcox <> | Subject | Re: Proof-of-concept: better(?) page-table manipulation API |
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On Tue, Apr 24, 2018 at 06:43:56PM +0300, Kirill A. Shutemov wrote: > +struct pt_ptr { > + unsigned long *ptr; > + int lvl; > +};
On x86, you've got three kinds of paging scheme, referred to in the manual as 32-bit, PAE and 4-level. On 32-bit, you've got 3 levels (Directory, Table and Entry), and you can encode those three levels in the bottom two bits of the pointer. With PAE and 4L, pointers are 64-bit aligned, so you can encode up to eight levels in the bottom three bits of the pointer.
> +struct pt_val { > + unsigned long val; > + int lvl; > +};
I don't think it's possible to shrink this down to a single ulong. _Maybe_ it is if you can squirm a single bit free from the !pte_present case.
... this is only for x86 4L and maybe 32 paging, right? It'd need to use unsigned long val[2] for PAE.
I'm going to think about this some more. There's a lot of potential here.
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