Re: [RFC PATCH 06/12] kvm-arm: Pass kvm parameter for pagetable helpers

Christoffer Dall
2016-03-22T10:29:02Z

On Tue, Mar 22, 2016 at 10:15:11AM +0000, Suzuki K. Poulose wrote:
> On 22/03/16 09:30, Christoffer Dall wrote:
> >On Mon, Mar 14, 2016 at 04:53:05PM +0000, Suzuki K Poulose wrote:
> >>Pass 'kvm' to existing kvm_p.d_* page table wrappers to prepare
> >>them to choose between hyp and stage2 page table. No functional
> >>changes yet. Also while at it, convert them to static inline
> >>functions.
> >
> >I have to say that I'm not really crazy about the idea of having common
> >hyp and stage2 code and having the pgtable macros change behavior
> >depending on the type.
> >
> >Is it not so that that host pgtable macros will always be valid for the
> >hyp mappings, because we have the same VA space available etc.? It's
> >just a matter of different page table entry attributes.
>
> Yes, host pgtable macros are still used for hyp mappings, when kvm == NULL.
> and we do use explicit accessors (stage2_xxx wherever possible with this series).
>
> >
> >Looking at arch/arm/kvm/mmu.c, it looks to me like we would get the
> >cleanest separation by separating stuff that touches hyp page tables
> >from stuff that touches stage2 page tables.
>
> OK. Here are the routines which deal with both types:
>
> unmap_range, unmap_p{u,m}ds, unmap_ptes, clear_p{g,u,m}_entry
>
> Duplicating them won't be that much of trouble.
>
> >Then you can get rid of the whole kvm_ prefix and directly use stage2
> >accessors (which you may want to consider renaming to s2_) directly.
>
> Right.
>
> >
> >I think we've seen in the past that the confusion from functions
> >potentially touching both hyp and stage2 page tables is a bad thing and
> >we should seek to avoid it.
>
> OK, I will respin the series with the proposed changes.
>
Great, thanks a lot!!

-Christoffer