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Message-ID: <edb721906354e26c26883edf5bce09690ca07d6d.camel@cyberus-technology.de>
Subject: Re: [RFC PATCH 4/4] drm/i915/gvt: move public gvt headers out into
 global include
From:   Julian Stecklina <julian.stecklina@cyberus-technology.de>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     intel-gvt-dev@lists.freedesktop.org,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        zhiyuan.lv@intel.com, hang.yuan@intel.com,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Thomas Prescher <thomas.prescher@cyberus-technology.de>
Date:   Thu, 16 Jan 2020 16:05:22 +0100
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Hi Greg,

On Thu, 2020-01-16 at 15:23 +0100, Greg KH wrote:
> On Thu, Jan 16, 2020 at 03:13:01PM +0100, Julian Stecklina wrote:
> > Hi Greg, Christoph,
> > 
> > On Wed, 2020-01-15 at 16:22 +0100, Greg KH wrote:
> > > On Thu, Jan 09, 2020 at 07:13:57PM +0200, Julian Stecklina wrote:
> > > > Now that the GVT interface to hypervisors does not depend on i915/GVT
> > > > internals anymore, we can move the headers to the global include/.
> > > > 
> > > > This makes out-of-tree modules for hypervisor integration possible.
> > > 
> > > What kind of out-of-tree modules do you need/want for this?
> > 
> > The mediated virtualization support in the i915 driver needs a backend to
> > the
> > hypervisor. There is currently one backend for KVM in the tree
> > (drivers/gpu/drm/i915/gvt/kvmgt.c) and at least 3 other hypervisor backends
> > out
> > of tree in various states of development that I know of. We are currently
> > developing one of these.
> 
> Great, then just submit this patch series as part of your patch series
> when submitting yoru hypervisor code.  That's the normal way to export
> new symbols, we can't do so without an in-kernel user.

Fair enough.

As I already said, the KVMGT code is the in-kernel user. But I guess I can
extend the already existing function pointer way of decoupling KVMGT from i915
and be on my way without exporting any symbols.

Somewhat independent of the current discussion, I also think that it's valuable
to have a defined API (I'm not saying stable API) for the hypervisor backends to
define what's okay and not okay for them to do.

Thanks,
Julian