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Subject: Re: [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow_pfn
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To:     Daniel Vetter <daniel.vetter@ffwll.ch>
Cc:     DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        KVM list <kvm@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@vger.kernel.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Kees Cook <keescook@chromium.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>,
        =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>,
        Jan Kara <jack@suse.cz>
References: <20201119144146.1045202-1-daniel.vetter@ffwll.ch>
 <20201119144146.1045202-17-daniel.vetter@ffwll.ch>
 <cd56eb8a-fbec-e81f-9c14-d1256a193b68@redhat.com>
 <CAKMK7uHDrPDcsWyMgFgjf0+hdebSUT4hX5hKR=CnTH=soLU-Kg@mail.gmail.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <3eca2dde-c78b-3eb4-8f61-7fdf16573419@redhat.com>
Date:   Fri, 20 Nov 2020 16:55:00 +0100
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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