Re: Linux 5.1.9 build failure with CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT=n

[Thomas Backlund]

Den 11-06-2019 kl. 20:40, skrev Greg Kroah-Hartman:
> 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@xxxxxxxxxxxxxxxxxxx> 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?

Or add the simple fix suggested by Daniel (if I understand correctly):


From: Thomas Backlund <tmb@xxxxxxxxxx>

Setting CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT=n (added by commit: 
b30a43ac7132) causes the build to fail with:

ERROR: "drm_legacy_mmap" [drivers/gpu/drm/nouveau/nouveau.ko] undefined!

Fix that by adding check for CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT around
the code using drm_legacy_mmap()

Fixes: b30a43ac7132 drm/nouveau: add kconfig option to turn off nouveau 
legacy contexts. (v3)
Signed-off-by: Thomas Backlund <tmb@xxxxxxxxxx>

---
 drivers/gpu/drm/nouveau/nouveau_ttm.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/gpu/drm/nouveau/nouveau_ttm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c
@@ -168,8 +168,10 @@ nouveau_ttm_mmap(struct file *filp, stru
 	struct drm_file *file_priv = filp->private_data;
 	struct nouveau_drm *drm = nouveau_drm(file_priv->minor->dev);

+#if defined(CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT)
 	if (unlikely(vma->vm_pgoff < DRM_FILE_PAGE_OFFSET))
 		return drm_legacy_mmap(filp, vma);
+#endif

 	return ttm_bo_mmap(filp, vma, &drm->ttm.bdev);
 }