On 17/03/2017 11:17, Borislav Petkov wrote:
>
>> I also don't really like the patch as is (plus it fails modpost), but
>> IMO reusing __change_page_attr and __split_large_page is the right thing
>> to do.
>
> Right, so teaching pageattr.c about memblock could theoretically come
> around and bite us later when a page allocated with memblock gets freed
> with free_page().
Theoretically or practically?
> And looking at this more, we have all this kernel pagetable preparation
> code down the init_mem_mapping() call and the pagetable setup in
> arch/x86/mm/init_{32,64}.c
It only looks at the E820 map, doesn't it? Why does it have to do
anything with percpu memory areas?
Paolo
> And that code even does some basic page splitting. Oh and it uses
> alloc_low_pages() which knows whether to do memblock reservation or the
> common __get_free_pages() when slabs are up.
>
> So what would be much cleaner, IMHO, is if one would reuse that code to
> change init_mm.pgd mappings early without copying pageattr.c.
>
> init_mem_mapping() gets called before kvm_guest_init() in setup_arch()
> so the guest would simply fixup its pagetable right there.
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