drm/i915: add prefault_disable module option

prefault is stll enabled by default which prevent most of pwrite/pread/reloc
from running slow path, in order to verify these slow pathes, prefault need
to be disabled.

Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
[danvet: Make checkpatch happy and bikeshed the module option help
text a bit.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

4 files changed, 17 insertions, 7 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index b178a7ca1294..c34086ad8181 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -141,6 +141,11 @@ module_param_named(fastboot, i915_fastboot, bool, 0600);
 MODULE_PARM_DESC(fastboot, "Try to skip unnecessary mode sets at boot time "
                  "(default: false)");
 
+bool i915_prefault_disable __read_mostly;
+module_param_named(prefault_disable, i915_prefault_disable, bool, 0600);
+MODULE_PARM_DESC(prefault_disable,
+                "Disable page prefaulting for pread/pwrite/reloc (default:false). For developers only.");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 36d1c806e092..fc32d2034f38 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1627,6 +1627,7 @@ extern unsigned int i915_preliminary_hw_support __read_mostly;
 extern int i915_disable_power_well __read_mostly;
 extern int i915_enable_ips __read_mostly;
 extern bool i915_fastboot __read_mostly;
+extern bool i915_prefault_disable __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ce043f14eab9..acc99d458143 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -465,7 +465,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
 
                 mutex_unlock(&dev->struct_mutex);
 
-                if (!prefaulted) {
+                if (likely(!i915_prefault_disable) && !prefaulted) {
                         ret = fault_in_multipages_writeable(user_data, remain);
                         /* Userspace is tricking us, but we've already clobbered
                          * its pages with the prefault and promised to write the
@@ -860,10 +860,12 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                        args->size))
                 return -EFAULT;
 
-        ret = fault_in_multipages_readable(to_user_ptr(args->data_ptr),
-                                           args->size);
-        if (ret)
-                return -EFAULT;
+        if (likely(!i915_prefault_disable)) {
+                ret = fault_in_multipages_readable(to_user_ptr(args->data_ptr),
+                                                   args->size);
+                if (ret)
+                        return -EFAULT;
+        }
 
         ret = i915_mutex_lock_interruptible(dev);
         if (ret)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 1b58694d7be7..1734825bef34 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -759,8 +759,10 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec,
                 if (!access_ok(VERIFY_WRITE, ptr, length))
                         return -EFAULT;
 
-                if (fault_in_multipages_readable(ptr, length))
-                        return -EFAULT;
+                if (likely(!i915_prefault_disable)) {
+                        if (fault_in_multipages_readable(ptr, length))
+                                return -EFAULT;
+                }
         }
 
         return 0;