Sparse DRM objects will store their backing pages in an xarray, to avoid the
overhead of preallocating a huge struct page pointer array when only a very
small range of indices might be assigned.
For now, only the definition of a sparse object as a union alternative to a
'dense' object is provided, with functions that exploit it being part of later
commits.
Signed-off-by: Adrián Larumbe <adrian.laru...@collabora.com>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 42 +++++++++++++++++++++++---
include/drm/drm_gem_shmem_helper.h | 18 ++++++++++-
2 files changed, 54 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 5ab351409312..d63e42be2d72 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -10,6 +10,7 @@
#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+#include <linux/xarray.h>
#ifdef CONFIG_X86
#include <asm/set_memory.h>
@@ -50,7 +51,7 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs
= {
static struct drm_gem_shmem_object *
__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private,
- struct vfsmount *gemfs)
+ bool sparse, struct vfsmount *gemfs)
{
struct drm_gem_shmem_object *shmem;
struct drm_gem_object *obj;
@@ -90,6 +91,11 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size,
bool private,
INIT_LIST_HEAD(&shmem->madv_list);
+ if (unlikely(sparse))
+ xa_init_flags(&shmem->xapages, XA_FLAGS_ALLOC);
+
+ shmem->sparse = sparse;
+
if (!private) {
/*
* Our buffers are kept pinned, so allocating them
@@ -124,10 +130,16 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t
size, bool private,
*/
struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev,
size_t size)
{
- return __drm_gem_shmem_create(dev, size, false, NULL);
+ return __drm_gem_shmem_create(dev, size, false, false, NULL);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
+struct drm_gem_shmem_object *drm_gem_shmem_create_sparse(struct drm_device
*dev, size_t size)
+{
+ return __drm_gem_shmem_create(dev, size, false, true, NULL);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_create_sparse);
+
/**
* drm_gem_shmem_create_with_mnt - Allocate an object with the given size in a
* given mountpoint
@@ -145,7 +157,7 @@ struct drm_gem_shmem_object
*drm_gem_shmem_create_with_mnt(struct drm_device *de
size_t size,
struct vfsmount
*gemfs)
{
- return __drm_gem_shmem_create(dev, size, false, gemfs);
+ return __drm_gem_shmem_create(dev, size, false, false, gemfs);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_create_with_mnt);
@@ -173,7 +185,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
sg_free_table(shmem->sgt);
kfree(shmem->sgt);
}
- if (shmem->pages)
+
+ if ((!shmem->sparse && shmem->pages) ||
+ (shmem->sparse && !xa_empty(&shmem->xapages)))
drm_gem_shmem_put_pages(shmem);
drm_WARN_ON(obj->dev, shmem->pages_use_count);
@@ -191,11 +205,19 @@ static int drm_gem_shmem_get_pages(struct
drm_gem_shmem_object *shmem)
struct drm_gem_object *obj = &shmem->base;
struct page **pages;
+ if (drm_WARN_ON(obj->dev, shmem->sparse))
+ return -EINVAL;
+
dma_resv_assert_held(shmem->base.resv);
if (shmem->pages_use_count++ > 0)
return 0;
+ /* We only allow increasing the user count in the case of
+ sparse shmem objects with some backed pages for now */
+ if (shmem->sparse && xa_empty(&shmem->xapages))
+ return -EINVAL;
+
pages = drm_gem_get_pages(obj);
if (IS_ERR(pages)) {
drm_dbg_kms(obj->dev, "Failed to get pages (%ld)\n",
@@ -541,6 +563,8 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
struct page *page;
pgoff_t page_offset;
+ drm_WARN_ON(obj->dev, shmem->sparse);
+
/* We don't use vmf->pgoff since that has the fake offset */
page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
@@ -567,6 +591,7 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct
*vma)
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
drm_WARN_ON(obj->dev, obj->import_attach);
+ drm_WARN_ON(obj->dev, shmem->sparse);
dma_resv_lock(shmem->base.resv, NULL);
@@ -666,6 +691,9 @@ void drm_gem_shmem_print_info(const struct
drm_gem_shmem_object *shmem,
if (shmem->base.import_attach)
return;
+ if (drm_WARN_ON(shmem->base.dev, shmem->sparse))
+ return;
+
drm_printf_indent(p, indent, "pages_use_count=%u\n",
shmem->pages_use_count);
drm_printf_indent(p, indent, "vmap_use_count=%u\n",
shmem->vmap_use_count);
drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
@@ -691,6 +719,7 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct
drm_gem_shmem_object *shmem)
struct drm_gem_object *obj = &shmem->base;
drm_WARN_ON(obj->dev, obj->import_attach);
+ drm_WARN_ON(obj->dev, shmem->sparse);
return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >>
PAGE_SHIFT);
}
@@ -702,6 +731,9 @@ static struct sg_table
*drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
int ret;
struct sg_table *sgt;
+ if (drm_WARN_ON(obj->dev, shmem->sparse))
+ return ERR_PTR(-EINVAL);
+
if (shmem->sgt)
return shmem->sgt;
@@ -787,7 +819,7 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
size_t size = PAGE_ALIGN(attach->dmabuf->size);
struct drm_gem_shmem_object *shmem;
- shmem = __drm_gem_shmem_create(dev, size, true, NULL);
+ shmem = __drm_gem_shmem_create(dev, size, true, false, NULL);
if (IS_ERR(shmem))
return ERR_CAST(shmem);
diff --git a/include/drm/drm_gem_shmem_helper.h
b/include/drm/drm_gem_shmem_helper.h
index d22e3fb53631..902039cfc4ce 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -6,6 +6,7 @@
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/mutex.h>
+#include <linux/xarray.h>
#include <drm/drm_file.h>
#include <drm/drm_gem.h>
@@ -29,7 +30,11 @@ struct drm_gem_shmem_object {
/**
* @pages: Page table
*/
- struct page **pages;
+ union {
+
+ struct page **pages;
+ struct xarray xapages;
+ };
/**
* @pages_use_count:
@@ -91,6 +96,11 @@ struct drm_gem_shmem_object {
* @map_wc: map object write-combined (instead of using shmem defaults).
*/
bool map_wc : 1;
+
+ /**
+ * @sparse: the object's virtual memory space is only partially backed
by pages
+ */
+ bool sparse : 1;
};
#define to_drm_gem_shmem_obj(obj) \
@@ -229,6 +239,9 @@ static inline int drm_gem_shmem_object_vmap(struct
drm_gem_object *obj,
{
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+ if (shmem->sparse)
+ return -EACCES;
+
return drm_gem_shmem_vmap(shmem, map);
}
@@ -263,6 +276,9 @@ static inline int drm_gem_shmem_object_mmap(struct
drm_gem_object *obj, struct v
{
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+ if (shmem->sparse)
+ return -EACCES;
+
return drm_gem_shmem_mmap(shmem, vma);
}
--
2.47.1
