linux-kernel - Re: [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow

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Message-ID: <3eca2dde-c78b-3eb4-8f61-7fdf16573419@redhat.com>
Date:   Fri, 20 Nov 2020 16:55:00 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kees Cook <keescook@...omium.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow_pfn
 callsites

On 20/11/20 16:44, Daniel Vetter wrote:
>> 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

Pushing the lookups down would be worse code and possibly introduce 
TOC/TOU races, so better avoid that.  Your patch is fine. :)

Paolo