Re: Linux 5.1.9 build failure with CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT=n

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Jun 11, 2019 at 07:33:16PM +0200, Daniel Vetter wrote:
> On Tue, Jun 11, 2019 at 5:37 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Tue, Jun 11, 2019 at 03:56:35PM +0200, Sven Joachim wrote:
> > > Commit 1e07d63749 ("drm/nouveau: add kconfig option to turn off nouveau
> > > legacy contexts. (v3)") has caused a build failure for me when I
> > > actually tried that option (CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT=n):
> > >
> > > ,----
> > > | Kernel: arch/x86/boot/bzImage is ready  (#1)
> > > |   Building modules, stage 2.
> > > |   MODPOST 290 modules
> > > | ERROR: "drm_legacy_mmap" [drivers/gpu/drm/nouveau/nouveau.ko] undefined!
> > > | scripts/Makefile.modpost:91: recipe for target '__modpost' failed
> > > `----
> 
> Calling drm_legacy_mmap is definitely not a great idea. I think either
> we need a custom patch to remove that out on older kernels, or maybe
> even #ifdef if you want to be super paranoid about breaking stuff ...
> 
> > > Upstream does not have that problem, as commit bed2dd8421 ("drm/ttm:
> > > Quick-test mmap offset in ttm_bo_mmap()") has removed the use of
> > > drm_legacy_mmap from nouveau_ttm.c.  Unfortunately that commit does not
> > > apply in 5.1.9.
> > >
> > > Most likely 4.19.50 and 4.14.125 are also affected, I haven't tested
> > > them yet.
> >
> > They probably are.
> >
> > Should I just revert this patch in the stable tree, or add some other
> > patch (like the one pointed out here, which seems an odd patch for
> > stable...)
> 
> ... or backport the above patch, that should be save to do too. Not
> sure what stable folks prefer?

The above patch does not apply to all of the stable branches, so how
about I just revert this?  People can live with this option not able to
turn off for now, and if they really want it, they can use a newer
kernel, right?

thanks,

greg k-h