linux-kernel - Re: revert dma direct internals abuse

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Message-ID: <a5643cb106797f7079c70d63f5031bdc01259bb0.camel@vmware.com>
Date:   Tue, 23 Apr 2019 12:26:05 +0000
From:   Thomas Hellstrom <thellstrom@...are.com>
To:     "hch@....de" <hch@....de>
CC:     "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Deepak Singh Rawat <drawat@...are.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: Re: revert dma direct internals abuse

Hi, Christoph,

On Mon, 2019-04-22 at 19:56 +0200, hch@....de wrote:
> On Wed, Apr 10, 2019 at 03:01:14PM +0000, Thomas Hellstrom wrote:
> > > So can you please respin a version acceptable to you and submit
> > > it
> > > for 5.1 ASAP?  Otherwise I'll need to move ahead with the simple
> > > revert.
> > 
> > I will. 
> > I need to do some testing to investigate how to best choose between
> > the
> > options, but will have something ready for 5.1.
> 
> I still don't see anything in -rc6..

Been on easter vacation. I have a patch ready for review, though, will
send it out in a moment.

It turns out that to do something well-behaved in case someone sets
swiotlb=force, the variable swiotlb_force would need to be exported.
(I can't rely on swiotlb_nr_tbl()).

That's not currently done in the patch, but instead the driver just
malfunctions like most other graphics drivers.

/Thomas