[RFC] drm/i915: Allow dmabuf mmap forwarding
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Mon Sep 25 13:16:38 UTC 2023
From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Allow mmap forwarding for imported buffers in order to allow minigbm mmap
to work on aperture-less platforms such as Meteorlake.
So far i915 did not allow mmap on imported buffers but from minigbm
perspective that worked because of the DRM_IOCTL_I915_GEM_MMAP_GTT fall-
back would then be attempted, and would be successful.
This stops working on Meteorlake since there is no aperture.
Allow i915 to mmap imported buffers using forwarding via dma_buf_mmap(),
which allows the primary minigbm path of DRM_IOCTL_I915_GEM_MMAP_OFFSET /
I915_MMAP_OFFSET_WB to work.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Christian König <christian.koenig at amd.com>
Cc: Matthew Auld <matthew.auld at intel.com>
Cc: Nirmoy Das <nirmoy.das at intel.com>
---
1)
It is unclear to me if any real userspace depends on this, but there are
certainly compliance suites which fail.
2)
It is also a bit unclear to me if dma_buf_mmap() is exactly intended for
this kind of use. It seems that it is, but I also found some old mailing
list discussions suggesting there might be some unresolved questions
around VMA revocation.
1 + 2 = RFC for now.
Daniel and Christian were involved in 2) in the past so comments would
be appreciated.
Test-with: 20230925131539.32743-1-tvrtko.ursulin at linux.intel.com
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 78 +++++++++++++++----
.../gpu/drm/i915/gem/i915_gem_object_types.h | 1 +
2 files changed, 65 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index aa4d842d4c5a..78c84c0a8b08 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -5,6 +5,7 @@
*/
#include <linux/anon_inodes.h>
+#include <linux/dma-buf.h>
#include <linux/mman.h>
#include <linux/pfn_t.h>
#include <linux/sizes.h>
@@ -664,6 +665,7 @@ insert_mmo(struct drm_i915_gem_object *obj, struct i915_mmap_offset *mmo)
static struct i915_mmap_offset *
mmap_offset_attach(struct drm_i915_gem_object *obj,
enum i915_mmap_type mmap_type,
+ bool forward_mmap,
struct drm_file *file)
{
struct drm_i915_private *i915 = to_i915(obj->base.dev);
@@ -682,6 +684,7 @@ mmap_offset_attach(struct drm_i915_gem_object *obj,
mmo->obj = obj;
mmo->mmap_type = mmap_type;
+ mmo->forward_mmap = forward_mmap;
drm_vma_node_reset(&mmo->vma_node);
err = drm_vma_offset_add(obj->base.dev->vma_offset_manager,
@@ -714,12 +717,25 @@ mmap_offset_attach(struct drm_i915_gem_object *obj,
return ERR_PTR(err);
}
+static bool
+should_forward_mmap(struct drm_i915_gem_object *obj,
+ enum i915_mmap_type mmap_type)
+{
+ if (!obj->base.import_attach)
+ return false;
+
+ return mmap_type == I915_MMAP_TYPE_WB ||
+ mmap_type == I915_MMAP_TYPE_WC ||
+ mmap_type == I915_MMAP_TYPE_UC;
+}
+
static int
__assign_mmap_offset(struct drm_i915_gem_object *obj,
enum i915_mmap_type mmap_type,
u64 *offset, struct drm_file *file)
{
struct i915_mmap_offset *mmo;
+ bool should_forward;
if (i915_gem_object_never_mmap(obj))
return -ENODEV;
@@ -735,12 +751,15 @@ __assign_mmap_offset(struct drm_i915_gem_object *obj,
if (mmap_type == I915_MMAP_TYPE_FIXED)
return -ENODEV;
+ should_forward = should_forward_mmap(obj, mmap_type);
+
if (mmap_type != I915_MMAP_TYPE_GTT &&
!i915_gem_object_has_struct_page(obj) &&
- !i915_gem_object_has_iomem(obj))
+ !i915_gem_object_has_iomem(obj) &&
+ !should_forward)
return -ENODEV;
- mmo = mmap_offset_attach(obj, mmap_type, file);
+ mmo = mmap_offset_attach(obj, mmap_type, should_forward, file);
if (IS_ERR(mmo))
return PTR_ERR(mmo);
@@ -936,6 +955,32 @@ static struct file *mmap_singleton(struct drm_i915_private *i915)
return file;
}
+static void
+__vma_mmap_pgprot(struct vm_area_struct *vma, enum i915_mmap_type mmap_type)
+{
+ const pgprot_t pgprot =vm_get_page_prot(vma->vm_flags);
+
+ switch (mmap_type) {
+ case I915_MMAP_TYPE_WC:
+ vma->vm_page_prot = pgprot_writecombine(pgprot);
+ break;
+ case I915_MMAP_TYPE_FIXED:
+ GEM_WARN_ON(1);
+ fallthrough;
+ case I915_MMAP_TYPE_WB:
+ vma->vm_page_prot = pgprot;
+ break;
+ case I915_MMAP_TYPE_UC:
+ vma->vm_page_prot = pgprot_noncached(pgprot);
+ break;
+ case I915_MMAP_TYPE_GTT:
+ vma->vm_page_prot = pgprot_writecombine(pgprot);
+ break;
+ }
+
+ vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
+}
+
static int
i915_gem_object_mmap(struct drm_i915_gem_object *obj,
struct i915_mmap_offset *mmo,
@@ -953,6 +998,20 @@ i915_gem_object_mmap(struct drm_i915_gem_object *obj,
vm_flags_clear(vma, VM_MAYWRITE);
}
+ /* dma-buf import */
+ if (mmo && mmo->forward_mmap) {
+ __vma_mmap_pgprot(vma, mmo->mmap_type);
+ vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP | VM_IO);
+
+ /*
+ * Don't have our vm_ops to drop the reference in this case so
+ * drop it now and if object goes away userspace will fault.
+ */
+ i915_gem_object_put(mmo->obj);
+
+ return dma_buf_mmap(obj->base.dma_buf, vma, 0);
+ }
+
anon = mmap_singleton(to_i915(dev));
if (IS_ERR(anon)) {
i915_gem_object_put(obj);
@@ -982,34 +1041,25 @@ i915_gem_object_mmap(struct drm_i915_gem_object *obj,
vma->vm_private_data = mmo;
+ __vma_mmap_pgprot(vma, mmo->mmap_type);
+
switch (mmo->mmap_type) {
case I915_MMAP_TYPE_WC:
- vma->vm_page_prot =
- pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
vma->vm_ops = &vm_ops_cpu;
break;
-
case I915_MMAP_TYPE_FIXED:
GEM_WARN_ON(1);
fallthrough;
case I915_MMAP_TYPE_WB:
- vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
vma->vm_ops = &vm_ops_cpu;
break;
-
case I915_MMAP_TYPE_UC:
- vma->vm_page_prot =
- pgprot_noncached(vm_get_page_prot(vma->vm_flags));
vma->vm_ops = &vm_ops_cpu;
break;
-
case I915_MMAP_TYPE_GTT:
- vma->vm_page_prot =
- pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
vma->vm_ops = &vm_ops_gtt;
break;
}
- vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
return 0;
}
@@ -1084,7 +1134,7 @@ int i915_gem_fb_mmap(struct drm_i915_gem_object *obj, struct vm_area_struct *vma
} else {
/* handle stolen and smem objects */
mmap_type = i915_ggtt_has_aperture(ggtt) ? I915_MMAP_TYPE_GTT : I915_MMAP_TYPE_WC;
- mmo = mmap_offset_attach(obj, mmap_type, NULL);
+ mmo = mmap_offset_attach(obj, mmap_type, false, NULL);
if (IS_ERR(mmo))
return PTR_ERR(mmo);
}
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 0c5cdab278b6..b4f86fa020aa 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -225,6 +225,7 @@ struct i915_mmap_offset {
struct drm_vma_offset_node vma_node;
struct drm_i915_gem_object *obj;
enum i915_mmap_type mmap_type;
+ bool forward_mmap;
struct rb_node offset;
};
--
2.39.2
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