Re: [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow_pfn callsites

[Daniel Vetter]

On Fri, Nov 20, 2020 at 4:33 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 19/11/20 15:41, Daniel Vetter wrote:
> > Both Christoph Hellwig and Jason Gunthorpe suggested that usage of
> > follow_pfn by modules should be locked down more. To do so callers
> > need to be able to pass the mmu_notifier subscription corresponding
> > to the mm_struct to follow_pfn().
> >
> > This patch does the rote work of doing that in the kvm subsystem. In
> > most places this is solved by passing struct kvm * down the call
> > stacks as an additional parameter, since that contains the
> > mmu_notifier.
> >
> > Compile tested on all affected arch.
>
> It's a bit of a pity, it's making an API more complex (the point of
> gfn_to_pfn_memslot vs gfn_to_pfn is exactly that you don't need a
> "struct kvm*" and it's clear that you've already done the lookup into
> that struct kvm.

Yeah I noticed that, I think pushing the lookups down should work, but
that's a fairly large-scale change. I didn't want to do that for the
RFC since it would distract from the actual change/goal.
-Daniel

> But it's not a big deal, and the rationale at least makes sense.  So,
>
> Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>
> Paolo



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch