linux-kernel - Re: [PATCH] vfio-mdev: reinstate VFIO

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Message-ID: <8A26B654-51D0-4007-919C-F1934BD0DFEE@nutanix.com>
Date: Thu, 12 Sep 2024 15:32:52 +0000
From: Jon Kohler <jon@...anix.com>
To: Christoph Hellwig <hch@....de>
CC: Kirti Wankhede <kwankhede@...dia.com>,
        Alex Williamson
	<alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, Tony Krowiak
	<akrowiak@...ux.ibm.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jason
 Gunthorpe <jgg@...dia.com>, Rohit Shenoy <rshenoy@...dia.com>,
        Tarun Gupta
	<targupta@...dia.com>
Subject: Re: [PATCH] vfio-mdev: reinstate VFIO_MDEV Kconfig



> On Sep 12, 2024, at 10:05 AM, Christoph Hellwig <hch@....de> wrote:
> 
> !-------------------------------------------------------------------|
>  CAUTION: External Email
> 
> |-------------------------------------------------------------------!
> 
> On Thu, Sep 12, 2024 at 07:19:55AM -0700, Jon Kohler wrote:
>> Reinstate Kconfig setup for CONFIG_VFIO_MDEV to help support out of
>> tree drivers that use VFIO_MDEV library (e.g. Nvidia GPU drivers).
> 
> NAK.  This is an internal symbol and the kernel could not care less
> about out of tree driver.  Get the drivers upstream if you care
> aboyut them.
> 

Christoph - thanks for the swift reply, I appreciate it. To clarify slightly,
MDEV does have various exported symbols in MDEV, with both regular
EXPORT_SYMBOL and _GPL variant; however, there is just no way to 
consume them out of tree without this patch, unless there is also
incidentally another in-tree module that has select VFIO_MDEV set.

Also, the kernel does have precedence for making changes
to support out of tree modules, as recent as this 6.11 cycle, example:
e188e5d5ffd ("s390/setup: Fix __pa/__va for modules under non-GPL licenses”)

I don’t want to rock the boat, I’m just trying to make sure I approach this
conversation correctly. 

While I’m on the thought, for the sake of cleanup, should exported in
drivers/vfio be _GPL variant? There is a bit of a mix now.

Thanks again for the review, 
Jon