linux-kernel - RE: [Patch v4 0/3] Introduce a driver to support host accelerated access to Microsoft Azure Blob

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Message-ID: <DM6PR21MB15138B5D5C8647C92EA6AB99CEE29@DM6PR21MB1513.namprd21.prod.outlook.com>
Date:   Tue, 20 Jul 2021 07:05:37 +0000
From:   Long Li <longli@...rosoft.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Bart Van Assche <bvanassche@....org>
CC:     "longli@...uxonhyperv.com" <longli@...uxonhyperv.com>,
        "linux-fs@...r.kernel.org" <linux-fs@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [Patch v4 0/3] Introduce a driver to support host accelerated
 access to Microsoft Azure Blob

> Subject: Re: [Patch v4 0/3] Introduce a driver to support host accelerated
> access to Microsoft Azure Blob
> 
> On Mon, Jul 19, 2021 at 09:37:56PM -0700, Bart Van Assche wrote:
> > such that this object storage driver can be implemented as a
> > user-space library instead of as a kernel driver? As you may know vfio
> > users can either use eventfds for completion notifications or polling.
> > An interface like io_uring can be built easily on top of vfio.
> 
> Yes.  Similar to say the NVMe K/V command set this does not look like a
> candidate for a kernel driver.

The driver is modeled to support multiple processes/users over a VMBUS
channel. I don't see a way that this can be implemented through VFIO? 

Even if it can be done, this exposes a security risk as the same VMBUS
channel is shared by multiple processes in user-mode.