linux-kernel - Re: [PATCH V3 2/4] misc: vop: do not allocate and reassign the used ring

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Date:   Thu, 29 Oct 2020 11:34:04 +0100
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Arnd Bergmann <arnd@...nel.org>, Sherry Sun <sherry.sun@....com>,
        "Dutt, Sudeep" <sudeep.dutt@...el.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "kishon@...com" <kishon@...com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "Dixit, Ashutosh" <ashutosh.dixit@...el.com>
Subject: Re: [PATCH V3 2/4] misc: vop: do not allocate and reassign the used
 ring

On Thu, Oct 29, 2020 at 11:07:27AM +0100, Vincent Whitchurch wrote:
> On Wed, Oct 28, 2020 at 04:50:36PM +0100, Arnd Bergmann wrote:
> > I think we should try to do something on top of the PCIe endpoint subsystem
> > to make it work across arbitrary combinations of host and device
> > implementations,
> > and provide a superset of what the MIC driver, (out-of-tree) Bluefield endpoint
> > driver, and the NTB subsystem as well as a couple of others used to do,
> > each of them tunneling block/network/serial/... over a PCIe link of some
> > sort, usually with virtio.
> 
> VOP is not PCIe-specific (as demonstrated by the vop-loopback patches I
> posted a while ago [1]), and it would be a shame for a replacement to be
> tied to the PCIe endpoint subsystem.  There are many SOCs out there
> which have multiple Linux-capable processors without cache-coherency
> between them.  VOP is (or should I say was since I guess it's being
> deleted) the closest we have in mainline to easily get generic virtio
> (and not just rpmsg) running between these kind of Linux instances.  If
> a new replacement framework were to be PCIe-exclusive then we'd have to
> invent one more framework for non-PCIe links to do pretty much the same
> thing.
> 
> [1] https://lore.kernel.org/lkml/20190403104746.16063-1-vincent.whitchurch@axis.com/

If this works well, please restore the existing code and move it to a
new directory and we can take it from there, right?

thanks,

greg k-h