Re: [PATCH 1/3] drm/i915: Set I915_BO_ALLOC_USER for framebuffer

[Matthew Auld]

On 06/03/2023 12:07, Nirmoy Das wrote:
Framebuffer is exposed to userspace so set I915_BO_ALLOC_USER
flag for it. This also make sure that ttm allocates offset
for lmem objects.
Signed-off-by: Nirmoy Das <nirmoy....@intel.com>
---
  drivers/gpu/drm/i915/display/intel_dpt.c           | 4 +++-
  drivers/gpu/drm/i915/display/intel_fbdev.c         | 3 ++-
  drivers/gpu/drm/i915/display/intel_plane_initial.c | 3 ++-
  3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dpt.c 
b/drivers/gpu/drm/i915/display/intel_dpt.c
index ad1a37b515fb..2e6238881860 100644
--- a/drivers/gpu/drm/i915/display/intel_dpt.c
+++ b/drivers/gpu/drm/i915/display/intel_dpt.c
@@ -254,7 +254,9 @@ intel_dpt_create(struct intel_framebuffer *fb)
  
  	size = round_up(size * sizeof(gen8_pte_t), I915_GTT_PAGE_SIZE);
  
-	dpt_obj = i915_gem_object_create_lmem(i915, size, I915_BO_ALLOC_CONTIGUOUS);
+       dpt_obj = i915_gem_object_create_lmem(i915, size,
+                                             I915_BO_ALLOC_CONTIGUOUS |
+                                             I915_BO_ALLOC_USER);

AFAICT this is just some driver internal stuff for display page-table, 
which gets mapped through GGTT or something, and is not the actual fb. 
Is it really exposed to the user?

        if (IS_ERR(dpt_obj) && i915_ggtt_has_aperture(to_gt(i915)->ggtt))
                dpt_obj = i915_gem_object_create_stolen(i915, size);
        if (IS_ERR(dpt_obj) && !HAS_LMEM(i915)) {
diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c 
b/drivers/gpu/drm/i915/display/intel_fbdev.c
index 3659350061a7..98ae3a3a986a 100644
--- a/drivers/gpu/drm/i915/display/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
@@ -163,7 +163,8 @@ static int intelfb_alloc(struct drm_fb_helper *helper,
        obj = ERR_PTR(-ENODEV);
        if (HAS_LMEM(dev_priv)) {
                obj = i915_gem_object_create_lmem(dev_priv, size,
-                                                 I915_BO_ALLOC_CONTIGUOUS);
+                                                 I915_BO_ALLOC_CONTIGUOUS |
+                                                 I915_BO_ALLOC_USER);
        } else {
                /*
                 * If the FB is too big, just don't use it since fbdev is not 
very
diff --git a/drivers/gpu/drm/i915/display/intel_plane_initial.c 
b/drivers/gpu/drm/i915/display/intel_plane_initial.c
index bb6ea7de5c61..4a3680f6a3f5 100644
--- a/drivers/gpu/drm/i915/display/intel_plane_initial.c
+++ b/drivers/gpu/drm/i915/display/intel_plane_initial.c
@@ -110,7 +110,8 @@ initial_plane_vma(struct drm_i915_private *i915,
            size * 2 > i915->dsm.usable_size)
                return NULL;
  
-	obj = i915_gem_object_create_region_at(mem, phys_base, size, 0);
+       obj = i915_gem_object_create_region_at(mem, phys_base, size,
+                                              I915_BO_ALLOC_USER);

ALLOC_USER has the side effect of also zeroing the memory underneath, 
IIRC. However this here is the pre-allocated fb (will have some boot 
logo stuff), so we shouldn't ever clear it.

        if (IS_ERR(obj))
                return NULL;