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Date:   Mon, 18 May 2020 09:50:44 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Satya Tangirala <satyat@google.com>,
        Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-scsi@vger.kernel.org, linux-fscrypt@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org,
        Barani Muthukumaran <bmuthuku@qti.qualcomm.com>,
        Kuohong Wang <kuohong.wang@mediatek.com>,
        Kim Boojin <boojin.kim@samsung.com>
Subject: Re: [PATCH v13 00/12] Inline Encryption Support
Message-ID: <20200518165044.GA23230@infradead.org>
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On Fri, May 15, 2020 at 10:00:59AM -0700, Eric Biggers wrote:
> The fallback is actually really useful.  First, for testing: it allows all the
> filesystem code that uses inline crypto to be tested using gce-xfstests and
> kvm-xfstests, so that it's covered by the usual ext4 and f2fs regression testing
> and it's much easier to develop patches for.  It also allowed us to enable the
> inlinecrypt mount option in Cuttlefish, which is the virtual Android device used
> to test the Android common kernels.  So, it gets the kernel test platform as
> similar to a real Android device as possible.
> 
> Ideally we'd implement virtualized inline encryption as you suggested.  But
> these platforms use a mix of VMM's (QEMU, GCE, and crosvm) and storage types
> (virtio-blk, virtio-scsi, and maybe others; none of these even have an inline
> encryption standard defined yet).  So it's not currently feasible.

Not that you don't need to implement it in the hypervisor.  You can
also trivially wire up for things like null_blk.

> Second, it creates a clean design where users can just use blk-crypto, and not
> have to implement a second encryption implementation.

And I very much disagree about that being a clean implementation.  It is
fine if the user doesn't care, but you should catch this before hitting
the block stack and do the encryption there without hardware blk-crypt
support.