[Intel-gfx] [PATCH 4/5] drm/i915/guc: Don't try to create log runtime if there is no log

[Michal Wajdeczko]

In case of GuC initialization failure we may continue with driver
load, but we wrongly assume that GuC is fully functional. This
leads to the BUG as we attempt to access non-existing log vma.

[26386.121085] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
[26386.121225] IP: guc_log_runtime_create+0x23/0xe0 [i915]
[26386.121763] Call Trace:
[26386.121870]  guc_log_late_setup+0xfd/0x140 [i915]
[26386.121969]  i915_driver_load+0x7ab/0x1730 [i915]
[26386.122069]  i915_pci_probe+0x2d/0x90 [i915]
[26386.122089]  pci_device_probe+0x9c/0x120
[26386.122107]  driver_probe_device+0x2a9/0x490
[26386.122126]  __driver_attach+0xd9/0xe0
[26386.122143]  ? driver_probe_device+0x490/0x490
[26386.122158]  bus_for_each_dev+0x57/0x90
[26386.122175]  bus_add_driver+0x1eb/0x260
[26386.122190]  ? 0xffffffffa069a000
[26386.122206]  driver_register+0x52/0xc0
[26386.122220]  ? 0xffffffffa069a000
[26386.122234]  do_one_initcall+0x39/0x170
[26386.122252]  ? kmem_cache_alloc_trace+0x1fd/0x2e0
[26386.122273]  do_init_module+0x56/0x1ec
[26386.122289]  load_module+0x219e/0x2550
[26386.122309]  ? vfs_read+0x121/0x140
[26386.122331]  ? SyS_finit_module+0xa5/0xe0
[26386.122346]  SyS_finit_module+0xa5/0xe0
[26386.122371]  entry_SYSCALL_64_fastpath+0x22/0x8f

Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski at intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble at intel.com>
---
 drivers/gpu/drm/i915/intel_guc_log.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_guc_log.c b/drivers/gpu/drm/i915/intel_guc_log.c
index 3fbe93a..fdb1895 100644
--- a/drivers/gpu/drm/i915/intel_guc_log.c
+++ b/drivers/gpu/drm/i915/intel_guc_log.c
@@ -395,6 +395,9 @@ static int guc_log_runtime_create(struct intel_guc *guc)
 	void *vaddr;
 	int ret;
 
+	if (!guc->log.vma)
+		return -ENODEV;
+
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
 	GEM_BUG_ON(guc_log_has_runtime(guc));
-- 
1.9.1