[Intel-gfx] [PATCH 1/3] drm/i915: add prefault_disable module option

[Xiong Zhang]

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 at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c            |  5 +++++
 drivers/gpu/drm/i915/i915_drv.h            |  1 +
 drivers/gpu/drm/i915/i915_gem.c            | 12 +++++++-----
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |  6 ++++--
 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 b07362f..dac6bd3 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -137,6 +137,11 @@ 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 = false;
+module_param_named(prefault_disable, i915_prefault_disable, bool, 0600);
+MODULE_PARM_DESC(prefault_disable,
+		"Try to disable pre page fault for pread/pwrite/reloc (default:false)");
+
 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 7fdc8e3..9516e19 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1587,6 +1587,7 @@ 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 c9d9d20..de59154 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 1b58694..1734825 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;
-- 
1.8.3.2