linux-kernel - [PATCH] drm/bochs: fix bochs_gem_prime

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Message-Id: <20190204183858.8976-1-kraxel@redhat.com>
Date:   Mon,  4 Feb 2019 19:38:58 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Gerd Hoffmann <kraxel@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org (open list:DRM DRIVER FOR
        BOCHS VIRTUAL GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/bochs: fix bochs_gem_prime_mmap

ttm_fbdev_mmap() just doesn't work.  It appears to work fine, mmap()
returns success, but any attempt to actually access the mapping causes a
SIGBUS.

We can just use drm_gem_prime_mmap() instead.  Almost.  We have to copy
over the start offset from the ttm_buffer_object vm_node to the
drm_gem_object vm_node so the offset math in drm_gem_prime_mmap() works
correctly for us even though we use ttm to manage our objects.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/gpu/drm/bochs/bochs_mm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bochs/bochs_mm.c b/drivers/gpu/drm/bochs/bochs_mm.c
index 641a33f134..49463348a0 100644
--- a/drivers/gpu/drm/bochs/bochs_mm.c
+++ b/drivers/gpu/drm/bochs/bochs_mm.c
@@ -442,5 +442,6 @@ int bochs_gem_prime_mmap(struct drm_gem_object *obj,
 {
 	struct bochs_bo *bo = gem_to_bochs_bo(obj);
 
-	return ttm_fbdev_mmap(vma, &bo->bo);
+	bo->gem.vma_node.vm_node.start = bo->bo.vma_node.vm_node.start;
+	return drm_gem_prime_mmap(obj, vma);
 }
-- 
2.9.3