drm/vgem: use shmem helpers

Aside from deleting lots of code the real motivation here is to switch
the mmap over to VM_PFNMAP, to be more consistent with what real gpu
drivers do. They're all VM_PFNMAP, which means get_user_pages doesn't
work, and even if you try and there's a struct page behind that,
touching it and mucking around with its refcount can upset drivers
real bad.

v2: Review from Thomas:
- sort #include
- drop more dead code that I didn't spot somehow

v3: select DRM_GEM_SHMEM_HELPER to make it build (intel-gfx-ci)

v4: I got tricked by 0cf2ef46c6c0 ("drm/shmem-helper: Use cached
mappings by default"), and we need WC in vgem because vgem doesn't
have explicit begin/end cpu access ioctls.

Also add a comment why exactly vgem has to use wc.

v5: Don't set obj->base.funcs, it will default to drm_gem_shmem_funcs
(Thomas)

v6: vgem also needs an MMU for remapping

v7: I absolutely butchered the rebases over the vgem mmap change and
revert and broke the patch. Actually go back to v6 from before the
vgem mmap changes.

Cc: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210812131412.2487363-4-daniel.vetter@ffwll.ch

2 files changed, 16 insertions, 331 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 314eefa39892..28f7d2006e8b 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -272,7 +272,8 @@ source "drivers/gpu/drm/kmb/Kconfig"
 
 config DRM_VGEM
 	tristate "Virtual GEM provider"
-	depends on DRM
+	depends on DRM && MMU
+	select DRM_GEM_SHMEM_HELPER
 	help
 	  Choose this option to get a virtual graphics memory manager,
 	  as used by Mesa's software renderer for enhanced performance.
@@ -280,7 +281,7 @@ config DRM_VGEM
 
 config DRM_VKMS
 	tristate "Virtual KMS (EXPERIMENTAL)"
-	depends on DRM
+	depends on DRM && MMU
 	select DRM_KMS_HELPER
 	select DRM_GEM_SHMEM_HELPER
 	select CRC32
diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index bf38a7e319d1..a87eafa89e9f 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -38,6 +38,7 @@
 
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
+#include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_ioctl.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_prime.h>
@@ -50,87 +51,11 @@
 #define DRIVER_MAJOR	1
 #define DRIVER_MINOR	0
 
-static const struct drm_gem_object_funcs vgem_gem_object_funcs;
-
 static struct vgem_device {
 	struct drm_device drm;
 	struct platform_device *platform;
 } *vgem_device;
 
-static void vgem_gem_free_object(struct drm_gem_object *obj)
-{
-	struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);
-
-	kvfree(vgem_obj->pages);
-	mutex_destroy(&vgem_obj->pages_lock);
-
-	if (obj->import_attach)
-		drm_prime_gem_destroy(obj, vgem_obj->table);
-
-	drm_gem_object_release(obj);
-	kfree(vgem_obj);
-}
-
-static vm_fault_t vgem_gem_fault(struct vm_fault *vmf)
-{
-	struct vm_area_struct *vma = vmf->vma;
-	struct drm_vgem_gem_object *obj = vma->vm_private_data;
-	/* We don't use vmf->pgoff since that has the fake offset */
-	unsigned long vaddr = vmf->address;
-	vm_fault_t ret = VM_FAULT_SIGBUS;
-	loff_t num_pages;
-	pgoff_t page_offset;
-	page_offset = (vaddr - vma->vm_start) >> PAGE_SHIFT;
-
-	num_pages = DIV_ROUND_UP(obj->base.size, PAGE_SIZE);
-
-	if (page_offset >= num_pages)
-		return VM_FAULT_SIGBUS;
-
-	mutex_lock(&obj->pages_lock);
-	if (obj->pages) {
-		get_page(obj->pages[page_offset]);
-		vmf->page = obj->pages[page_offset];
-		ret = 0;
-	}
-	mutex_unlock(&obj->pages_lock);
-	if (ret) {
-		struct page *page;
-
-		page = shmem_read_mapping_page(
-					file_inode(obj->base.filp)->i_mapping,
-					page_offset);
-		if (!IS_ERR(page)) {
-			vmf->page = page;
-			ret = 0;
-		} else switch (PTR_ERR(page)) {
-			case -ENOSPC:
-			case -ENOMEM:
-				ret = VM_FAULT_OOM;
-				break;
-			case -EBUSY:
-				ret = VM_FAULT_RETRY;
-				break;
-			case -EFAULT:
-			case -EINVAL:
-				ret = VM_FAULT_SIGBUS;
-				break;
-			default:
-				WARN_ON(PTR_ERR(page));
-				ret = VM_FAULT_SIGBUS;
-				break;
-		}
-
-	}
-	return ret;
-}
-
-static const struct vm_operations_struct vgem_gem_vm_ops = {
-	.fault = vgem_gem_fault,
-	.open = drm_gem_vm_open,
-	.close = drm_gem_vm_close,
-};
-
 static int vgem_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct vgem_file *vfile;
@@ -159,266 +84,30 @@ static void vgem_postclose(struct drm_device *dev, struct drm_file *file)
 	kfree(vfile);
 }
 
-static struct drm_vgem_gem_object *__vgem_gem_create(struct drm_device *dev,
-						unsigned long size)
-{
-	struct drm_vgem_gem_object *obj;
-	int ret;
-
-	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
-	if (!obj)
-		return ERR_PTR(-ENOMEM);
-
-	obj->base.funcs = &vgem_gem_object_funcs;
-
-	ret = drm_gem_object_init(dev, &obj->base, roundup(size, PAGE_SIZE));
-	if (ret) {
-		kfree(obj);
-		return ERR_PTR(ret);
-	}
-
-	mutex_init(&obj->pages_lock);
-
-	return obj;
-}
-
-static void __vgem_gem_destroy(struct drm_vgem_gem_object *obj)
-{
-	drm_gem_object_release(&obj->base);
-	kfree(obj);
-}
-
-static struct drm_gem_object *vgem_gem_create(struct drm_device *dev,
-					      struct drm_file *file,
-					      unsigned int *handle,
-					      unsigned long size)
-{
-	struct drm_vgem_gem_object *obj;
-	int ret;
-
-	obj = __vgem_gem_create(dev, size);
-	if (IS_ERR(obj))
-		return ERR_CAST(obj);
-
-	ret = drm_gem_handle_create(file, &obj->base, handle);
-	if (ret) {
-		drm_gem_object_put(&obj->base);
-		return ERR_PTR(ret);
-	}
-
-	return &obj->base;
-}
-
-static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
-				struct drm_mode_create_dumb *args)
-{
-	struct drm_gem_object *gem_object;
-	u64 pitch, size;
-
-	pitch = args->width * DIV_ROUND_UP(args->bpp, 8);
-	size = args->height * pitch;
-	if (size == 0)
-		return -EINVAL;
-
-	gem_object = vgem_gem_create(dev, file, &args->handle, size);
-	if (IS_ERR(gem_object))
-		return PTR_ERR(gem_object);
-
-	args->size = gem_object->size;
-	args->pitch = pitch;
-
-	drm_gem_object_put(gem_object);
-
-	DRM_DEBUG("Created object of size %llu\n", args->size);
-
-	return 0;
-}
-
 static struct drm_ioctl_desc vgem_ioctls[] = {
 	DRM_IOCTL_DEF_DRV(VGEM_FENCE_ATTACH, vgem_fence_attach_ioctl, DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(VGEM_FENCE_SIGNAL, vgem_fence_signal_ioctl, DRM_RENDER_ALLOW),
 };
 
-static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
-{
-	unsigned long flags = vma->vm_flags;
-	int ret;
-
-	ret = drm_gem_mmap(filp, vma);
-	if (ret)
-		return ret;
-
-	/* Keep the WC mmaping set by drm_gem_mmap() but our pages
-	 * are ordinary and not special.
-	 */
-	vma->vm_flags = flags | VM_DONTEXPAND | VM_DONTDUMP;
-	return 0;
-}
+DEFINE_DRM_GEM_FOPS(vgem_driver_fops);
 
-static const struct file_operations vgem_driver_fops = {
-	.owner		= THIS_MODULE,
-	.open		= drm_open,
-	.mmap		= vgem_mmap,
-	.poll		= drm_poll,
-	.read		= drm_read,
-	.unlocked_ioctl = drm_ioctl,
-	.compat_ioctl	= drm_compat_ioctl,
-	.release	= drm_release,
-};
-
-static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
-{
-	mutex_lock(&bo->pages_lock);
-	if (bo->pages_pin_count++ == 0) {
-		struct page **pages;
-
-		pages = drm_gem_get_pages(&bo->base);
-		if (IS_ERR(pages)) {
-			bo->pages_pin_count--;
-			mutex_unlock(&bo->pages_lock);
-			return pages;
-		}
-
-		bo->pages = pages;
-	}
-	mutex_unlock(&bo->pages_lock);
-
-	return bo->pages;
-}
-
-static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
-{
-	mutex_lock(&bo->pages_lock);
-	if (--bo->pages_pin_count == 0) {
-		drm_gem_put_pages(&bo->base, bo->pages, true, true);
-		bo->pages = NULL;
-	}
-	mutex_unlock(&bo->pages_lock);
-}
-
-static int vgem_prime_pin(struct drm_gem_object *obj)
+static struct drm_gem_object *vgem_gem_create_object(struct drm_device *dev, size_t size)
 {
-	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-	long n_pages = obj->size >> PAGE_SHIFT;
-	struct page **pages;
+	struct drm_gem_shmem_object *obj;
 
-	pages = vgem_pin_pages(bo);
-	if (IS_ERR(pages))
-		return PTR_ERR(pages);
+	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return NULL;
 
-	/* Flush the object from the CPU cache so that importers can rely
-	 * on coherent indirect access via the exported dma-address.
+	/*
+	 * vgem doesn't have any begin/end cpu access ioctls, therefore must use
+	 * coherent memory or dma-buf sharing just wont work.
 	 */
-	drm_clflush_pages(pages, n_pages);
-
-	return 0;
-}
-
-static void vgem_prime_unpin(struct drm_gem_object *obj)
-{
-	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-
-	vgem_unpin_pages(bo);
-}
-
-static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
-{
-	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-
-	return drm_prime_pages_to_sg(obj->dev, bo->pages, bo->base.size >> PAGE_SHIFT);
-}
-
-static struct drm_gem_object* vgem_prime_import(struct drm_device *dev,
-						struct dma_buf *dma_buf)
-{
-	struct vgem_device *vgem = container_of(dev, typeof(*vgem), drm);
-
-	return drm_gem_prime_import_dev(dev, dma_buf, &vgem->platform->dev);
-}
-
-static struct drm_gem_object *vgem_prime_import_sg_table(struct drm_device *dev,
-			struct dma_buf_attachment *attach, struct sg_table *sg)
-{
-	struct drm_vgem_gem_object *obj;
-	int npages;
-
-	obj = __vgem_gem_create(dev, attach->dmabuf->size);
-	if (IS_ERR(obj))
-		return ERR_CAST(obj);
+	obj->map_wc = true;
 
-	npages = PAGE_ALIGN(attach->dmabuf->size) / PAGE_SIZE;
-
-	obj->table = sg;
-	obj->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
-	if (!obj->pages) {
-		__vgem_gem_destroy(obj);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	obj->pages_pin_count++; /* perma-pinned */
-	drm_prime_sg_to_page_array(obj->table, obj->pages, npages);
 	return &obj->base;
 }
 
-static int vgem_prime_vmap(struct drm_gem_object *obj, struct dma_buf_map *map)
-{
-	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-	long n_pages = obj->size >> PAGE_SHIFT;
-	struct page **pages;
-	void *vaddr;
-
-	pages = vgem_pin_pages(bo);
-	if (IS_ERR(pages))
-		return PTR_ERR(pages);
-
-	vaddr = vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL));
-	if (!vaddr)
-		return -ENOMEM;
-	dma_buf_map_set_vaddr(map, vaddr);
-
-	return 0;
-}
-
-static void vgem_prime_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map)
-{
-	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-
-	vunmap(map->vaddr);
-	vgem_unpin_pages(bo);
-}
-
-static int vgem_prime_mmap(struct drm_gem_object *obj,
-			   struct vm_area_struct *vma)
-{
-	int ret;
-
-	if (obj->size < vma->vm_end - vma->vm_start)
-		return -EINVAL;
-
-	if (!obj->filp)
-		return -ENODEV;
-
-	ret = call_mmap(obj->filp, vma);
-	if (ret)
-		return ret;
-
-	vma_set_file(vma, obj->filp);
-	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
-	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
-
-	return 0;
-}
-
-static const struct drm_gem_object_funcs vgem_gem_object_funcs = {
-	.free = vgem_gem_free_object,
-	.pin = vgem_prime_pin,
-	.unpin = vgem_prime_unpin,
-	.get_sg_table = vgem_prime_get_sg_table,
-	.vmap = vgem_prime_vmap,
-	.vunmap = vgem_prime_vunmap,
-	.vm_ops = &vgem_gem_vm_ops,
-};
-
 static const struct drm_driver vgem_driver = {
 	.driver_features		= DRIVER_GEM | DRIVER_RENDER,
 	.open				= vgem_open,
@@ -427,13 +116,8 @@ static const struct drm_driver vgem_driver = {
 	.num_ioctls 			= ARRAY_SIZE(vgem_ioctls),
 	.fops				= &vgem_driver_fops,
 
-	.dumb_create			= vgem_gem_dumb_create,
-
-	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
-	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
-	.gem_prime_import = vgem_prime_import,
-	.gem_prime_import_sg_table = vgem_prime_import_sg_table,
-	.gem_prime_mmap = vgem_prime_mmap,
+	DRM_GEM_SHMEM_DRIVER_OPS,
+	.gem_create_object		= vgem_gem_create_object,
 
 	.name	= DRIVER_NAME,
 	.desc	= DRIVER_DESC,