linux-kernel - Re: [PATCH 1/2] mm: provide a sane PTE walking API for modules

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Message-ID: <d238b495-dbae-1bc4-3397-5bceadfddb7e@redhat.com>
Date:   Tue, 9 Feb 2021 10:19:33 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org, jgg@...pe.ca,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        dan.j.williams@...el.com, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH 1/2] mm: provide a sane PTE walking API for modules

On 09/02/21 09:14, Christoph Hellwig wrote:
> On Mon, Feb 08, 2021 at 07:18:56PM +0100, Paolo Bonzini wrote:
>> Fair enough.  I would expect that pretty much everyone using follow_pfn will
>> at least want to switch to this one (as it's less bad and not impossible to
>> use correctly), but I'll squash this in:
> 
> 
> Daniel looked into them, so he may correct me, but the other follow_pfn
> users and their destiny are:
> 
>   - SGX, which is not modular and I think I just saw a patch to kill them
>   - v4l videobuf and frame vector: I think those are going away
>     entirely as they implement a rather broken pre-dmabuf P2P scheme
>   - vfio: should use MMU notifiers eventually

Yes, I'm thinking mostly of vfio, which could use follow_pte as a 
short-term fix for just the missing permission check.

There's also s390 PCI, which is also not modular.

Paolo

> Daniel, what happened to your follow_pfn series?