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Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
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>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     kvm@vger.kernel.org, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, 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>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <cd56eb8a-fbec-e81f-9c14-d1256a193b68@redhat.com>
Date:   Fri, 20 Nov 2020 16:33:44 +0100
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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.

But it's not a big deal, and the rationale at least makes sense.  So,

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo