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Date:   Fri, 17 Aug 2018 09:10:09 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Michal Wnukowski <wnukowski@google.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        keith.busch@linux.intel.com, Jens Axboe <axboe@fb.com>,
        Sagi Grimberg <sagi@grimberg.me>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-nvme <linux-nvme@lists.infradead.org>,
        Keith Busch <keith.busch@intel.com>, yigitfiliz@google.com,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] Bugfix for handling of shadow doorbell buffer.
Message-ID: <20180817071009.GB11383@lst.de>
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On Tue, Aug 14, 2018 at 06:35:16PM -0700, Michal Wnukowski wrote:
> 
> The other side in this case is not actual controller hardware, but 
> virtual one (the regular hardware should rely on normal MMIO 
> doorbells).

There could very much be real hardware there.  We've made it clear
in the spec that while a typical use case is a virtualized controller
there is nothing peventing hardware implementations.  There have
been previous hardware prototypes to use very similar tricks, e.g.:

https://www.usenix.org/node/179878