[Intel-gfx] [PATCH] drm/i915: Fail to load driver if KMS request without GEM

[Chris Wilson]

The i915's implementation of KMS requires GEM in order to manage the
memory and execution domains of the framebuffer and associated
resources. By the point at which we detect broken a BIOS and need to
disable GEM, we have already registered ourselves as a KMS driver with
several subsystems. Rather than introducing a fragile unwind and attempt
to continue with UMS, spit out an error and unload the driver.

References:

  [Bug 15754] IP: [<ffffffffa0207589>] drm_mm_search_free+0x49/0x90 [drm]
              BUG: unable to handle kernel NULL pointer dereference at (null)
  https://bugzilla.kernel.org/show_bug.cgi?id=15754

[drm:i915_driver_load] *ERROR* Detected broken video BIOS with
262140/262144kB of video memory stolen.
[drm:i915_driver_load] *ERROR* Disabling GEM. (try reducing stolen
memory or updating the BIOS to fix).
i915 0000:00:02.0: irq 30 for MSI/MSI-X
[drm] set up 255M of stolen space
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffa0207589>] drm_mm_search_free+0x49/0x90 [drm]
PGD 69719067 PUD 69dda067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
last sysfs file: /sys/module/snd_seq_oss/initstate
CPU 1
Pid: 867, comm: modprobe Not tainted 2.6.33-ARCH #1 G43Twins-FullHD/To
Be Filled By O.E.M.
RIP: 0010:[<ffffffffa0207589>]  [<ffffffffa0207589>] drm_mm_search_free+0x49/0x90 [drm]
RSP: 0018:ffff8800699f3af8  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffffffffffff RCX: 0000000000000000
RDX: 0000000000001000 RSI: 0000000000001000 RDI: ffff8800693d0f78
RBP: ffff8800699f3b18 R08: 0000000000001000 R09: 0000000000000000
R10: 2222222222222222 R11: 0000000000000000 R12: ffff880068de70c0
R13: 0000000000001000 R14: 0000000000000000 R15: ffff8800689cb000
FS:  00007fa93f4e5700(0000) GS:ffff880001880000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000695a0000 CR4: 00000000000406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process modprobe (pid: 867, threadinfo ffff8800699f2000, task ffff8800694f4740)
Stack:
 ffff880068de73c0 ffff880068de70c0 ffff8800689cb000 0000000000001000
<0> ffff8800699f3b68 ffffffffa0299f63 ffff8800693d0f78 0000120068de70c0
<0> ffff8800689cb000 ffff880068de73c0 ffff880068de70c0 ffff8800689cb000
Call Trace:
 [<ffffffffa0299f63>] i915_gem_object_bind_to_gtt+0x83/0x360 [i915]
 [<ffffffffa029a2e5>] i915_gem_object_pin+0xa5/0xb0 [i915]
 [<ffffffffa029a3c5>] i915_gem_init_ringbuffer+0xd5/0x510 [i915]
 [<ffffffffa028dbee>] i915_driver_load+0x4ce/0xd00 [i915]
 [<ffffffffa0205d37>] ? drm_sysfs_device_add+0x87/0xb0 [drm]
 [<ffffffffa0203363>] ? drm_get_minor+0x1d3/0x330 [drm]
 [<ffffffffa02037e6>] drm_get_dev+0x326/0x580 [drm]
 [<ffffffffa02bc0a5>] i915_pci_probe+0x10/0xd0 [i915]
 [<ffffffff811e98a2>] local_pci_probe+0x12/0x20
 [<ffffffff811ea8e0>] pci_device_probe+0x80/0xb0
 [<ffffffff8127b12a>] ? driver_sysfs_add+0x5a/0x90
 [<ffffffff8127b273>] driver_probe_device+0x93/0x1a0
 [<ffffffff8127b413>] __driver_attach+0x93/0xa0
 [<ffffffff8127b380>] ? __driver_attach+0x0/0xa0
 [<ffffffff8127a8f8>] bus_for_each_dev+0x68/0x90
 [<ffffffff8127b0c9>] driver_attach+0x19/0x20
 [<ffffffff8127a0ad>] bus_add_driver+0xcd/0x2d0
 [<ffffffff8127b718>] driver_register+0x78/0x140
 [<ffffffff811eab91>] __pci_register_driver+0x51/0xd0
 [<ffffffffa02d6000>] ? i915_init+0x0/0x52 [i915]
 [<ffffffffa01fdc31>] drm_init+0x111/0x120 [drm]
 [<ffffffff810eb0cd>] ? register_shrinker+0x4d/0x60
 [<ffffffffa02d6000>] ? i915_init+0x0/0x52 [i915]
 [<ffffffffa02d6050>] i915_init+0x50/0x52 [i915]
 [<ffffffff81002047>] do_one_initcall+0x37/0x1a0
 [<ffffffff8108ed17>] sys_init_module+0xd7/0x250
 [<ffffffff81009fc2>] system_call_fastpath+0x16/0x1b
Code: eb 29 49 8b 41 28 31 d2 49 f7 f5 85 d2 74 39 44 89 c0 29 d0 48 89 c2 48 01 f2 49 39 d2 73 29 0f 1f 00 49 89 da 4c 89 d3 4d 89 d9 <4d> 8b 19 49 39 f9 41 0f 18 0b 74 2b 4d 8b 51 30 4d 89 cc 49 39
RIP  [<ffffffffa0207589>] drm_mm_search_free+0x49/0x90 [drm]
 RSP <ffff8800699f3af8>
CR2: 0000000000000000

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_dma.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 851a2f8..39a685e 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1672,6 +1672,13 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 		dev_priv->has_gem = 0;
 	}
 
+	if (dev_priv->has_gem == 0 &&
+	    drm_core_check_feature(dev, DRIVER_MODESET)) {
+		DRM_ERROR("kernel modesetting requires GEM, disabling driver.\n");
+		ret = -ENODEV;
+		goto out_iomapfree;
+	}
+
 	dev->driver->get_vblank_counter = i915_get_vblank_counter;
 	dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
 	if (IS_G4X(dev) || IS_IRONLAKE(dev) || IS_GEN6(dev)) {
-- 
1.7.1