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Commit fbb0de79 authored by Gerd Hoffmann's avatar Gerd Hoffmann
Browse files

Add udmabuf misc device 

A driver to let userspace turn memfd regions into dma-bufs.

Use case:  Allows qemu create dmabufs for the vga framebuffer or
virtio-gpu ressources.  Then they can be passed around to display
those guest things on the host.  To spice client for classic full
framebuffer display, and hopefully some day to wayland server for
seamless guest window display.

qemu test branch:
  https://git.kraxel.org/cgit/qemu/log/?h=sirius/udmabuf



Cc: David Airlie <airlied@linux.ie>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20180827093444.23623-1-kraxel@redhat.com
parent b972cece

Documentation/ioctl/ioctl-number.txt

+1 −0
Original line number Diff line number Diff line
@@ -272,6 +272,7 @@ Code Seq#(hex) Include File Comments 
't'	90-91	linux/toshiba.h		toshiba and toshiba_acpi SMM

'u'	00-1F	linux/smb_fs.h		gone

'u'	20-3F	linux/uvcvideo.h	USB video class host driver

'u'	40-4f	linux/udmabuf.h		userspace dma-buf misc device

'v'	00-1F	linux/ext2_fs.h		conflict!

'v'	00-1F	linux/fs.h		conflict!

'v'	00-0F	linux/sonypi.h		conflict!

MAINTAINERS

+8 −0
Original line number Diff line number Diff line
@@ -15343,6 +15343,14 @@ F: arch/x86/um/ 
F:	fs/hostfs/

F:	fs/hppfs/



USERSPACE DMA BUFFER DRIVER

M:	Gerd Hoffmann <kraxel@redhat.com>

S:	Maintained

L:	dri-devel@lists.freedesktop.org

F:	drivers/dma-buf/udmabuf.c

F:	include/uapi/linux/udmabuf.h

T:	git git://anongit.freedesktop.org/drm/drm-misc



USERSPACE I/O (UIO)

M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>

S:	Maintained

drivers/dma-buf/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -30,4 +30,12 @@ config SW_SYNC 
	  WARNING: improper use of this can result in deadlocking kernel

	  drivers from userspace. Intended for test and debug only.



config UDMABUF

	bool "userspace dmabuf misc driver"

	default n

	depends on DMA_SHARED_BUFFER

	help

	  A driver to let userspace turn memfd regions into dma-bufs.

	  Qemu can use this to create host dmabufs for guest framebuffers.



endmenu

drivers/dma-buf/Makefile

+1 −0
Original line number Diff line number Diff line 
obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o

obj-$(CONFIG_SYNC_FILE)		+= sync_file.o

obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o

obj-$(CONFIG_UDMABUF)		+= udmabuf.o

drivers/dma-buf/udmabuf.c

0 → 100644
+287 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/init.h>

#include <linux/module.h>

#include <linux/device.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/miscdevice.h>

#include <linux/dma-buf.h>

#include <linux/highmem.h>

#include <linux/cred.h>

#include <linux/shmem_fs.h>

#include <linux/memfd.h>



#include <uapi/linux/udmabuf.h>



struct udmabuf {

	u32 pagecount;

	struct page **pages;

};



static int udmabuf_vm_fault(struct vm_fault *vmf)

{

	struct vm_area_struct *vma = vmf->vma;

	struct udmabuf *ubuf = vma->vm_private_data;



	if (WARN_ON(vmf->pgoff >= ubuf->pagecount))

		return VM_FAULT_SIGBUS;



	vmf->page = ubuf->pages[vmf->pgoff];

	get_page(vmf->page);

	return 0;

}



static const struct vm_operations_struct udmabuf_vm_ops = {

	.fault = udmabuf_vm_fault,

};



static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)

{

	struct udmabuf *ubuf = buf->priv;



	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)

		return -EINVAL;



	vma->vm_ops = &udmabuf_vm_ops;

	vma->vm_private_data = ubuf;

	return 0;

}



static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,

				    enum dma_data_direction direction)

{

	struct udmabuf *ubuf = at->dmabuf->priv;

	struct sg_table *sg;



	sg = kzalloc(sizeof(*sg), GFP_KERNEL);

	if (!sg)

		goto err1;

	if (sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->pagecount,

				      0, ubuf->pagecount << PAGE_SHIFT,

				      GFP_KERNEL) < 0)

		goto err2;

	if (!dma_map_sg(at->dev, sg->sgl, sg->nents, direction))

		goto err3;



	return sg;



err3:

	sg_free_table(sg);

err2:

	kfree(sg);

err1:

	return ERR_PTR(-ENOMEM);

}



static void unmap_udmabuf(struct dma_buf_attachment *at,

			  struct sg_table *sg,

			  enum dma_data_direction direction)

{

	sg_free_table(sg);

	kfree(sg);

}



static void release_udmabuf(struct dma_buf *buf)

{

	struct udmabuf *ubuf = buf->priv;

	pgoff_t pg;



	for (pg = 0; pg < ubuf->pagecount; pg++)

		put_page(ubuf->pages[pg]);

	kfree(ubuf->pages);

	kfree(ubuf);

}



static void *kmap_udmabuf(struct dma_buf *buf, unsigned long page_num)

{

	struct udmabuf *ubuf = buf->priv;

	struct page *page = ubuf->pages[page_num];



	return kmap(page);

}



static void kunmap_udmabuf(struct dma_buf *buf, unsigned long page_num,

			   void *vaddr)

{

	kunmap(vaddr);

}



static struct dma_buf_ops udmabuf_ops = {

	.map_dma_buf	  = map_udmabuf,

	.unmap_dma_buf	  = unmap_udmabuf,

	.release	  = release_udmabuf,

	.map		  = kmap_udmabuf,

	.unmap		  = kunmap_udmabuf,

	.mmap		  = mmap_udmabuf,

};



#define SEALS_WANTED (F_SEAL_SHRINK)

#define SEALS_DENIED (F_SEAL_WRITE)



static long udmabuf_create(struct udmabuf_create_list *head,

			   struct udmabuf_create_item *list)

{

	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

	struct file *memfd = NULL;

	struct udmabuf *ubuf;

	struct dma_buf *buf;

	pgoff_t pgoff, pgcnt, pgidx, pgbuf;

	struct page *page;

	int seals, ret = -EINVAL;

	u32 i, flags;



	ubuf = kzalloc(sizeof(struct udmabuf), GFP_KERNEL);

	if (!ubuf)

		return -ENOMEM;



	for (i = 0; i < head->count; i++) {

		if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))

			goto err_free_ubuf;

		if (!IS_ALIGNED(list[i].size, PAGE_SIZE))

			goto err_free_ubuf;

		ubuf->pagecount += list[i].size >> PAGE_SHIFT;

	}

	ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(struct page *),

				    GFP_KERNEL);

	if (!ubuf->pages) {

		ret = -ENOMEM;

		goto err_free_ubuf;

	}



	pgbuf = 0;

	for (i = 0; i < head->count; i++) {

		memfd = fget(list[i].memfd);

		if (!memfd)

			goto err_put_pages;

		if (!shmem_mapping(file_inode(memfd)->i_mapping))

			goto err_put_pages;

		seals = memfd_fcntl(memfd, F_GET_SEALS, 0);

		if (seals == -EINVAL ||

		    (seals & SEALS_WANTED) != SEALS_WANTED ||

		    (seals & SEALS_DENIED) != 0)

			goto err_put_pages;

		pgoff = list[i].offset >> PAGE_SHIFT;

		pgcnt = list[i].size   >> PAGE_SHIFT;

		for (pgidx = 0; pgidx < pgcnt; pgidx++) {

			page = shmem_read_mapping_page(

				file_inode(memfd)->i_mapping, pgoff + pgidx);

			if (IS_ERR(page)) {

				ret = PTR_ERR(page);

				goto err_put_pages;

			}

			ubuf->pages[pgbuf++] = page;

		}

		fput(memfd);

	}

	memfd = NULL;



	exp_info.ops  = &udmabuf_ops;

	exp_info.size = ubuf->pagecount << PAGE_SHIFT;

	exp_info.priv = ubuf;



	buf = dma_buf_export(&exp_info);

	if (IS_ERR(buf)) {

		ret = PTR_ERR(buf);

		goto err_put_pages;

	}



	flags = 0;

	if (head->flags & UDMABUF_FLAGS_CLOEXEC)

		flags |= O_CLOEXEC;

	return dma_buf_fd(buf, flags);



err_put_pages:

	while (pgbuf > 0)

		put_page(ubuf->pages[--pgbuf]);

err_free_ubuf:

	fput(memfd);

	kfree(ubuf->pages);

	kfree(ubuf);

	return ret;

}



static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)

{

	struct udmabuf_create create;

	struct udmabuf_create_list head;

	struct udmabuf_create_item list;



	if (copy_from_user(&create, (void __user *)arg,

			   sizeof(struct udmabuf_create)))

		return -EFAULT;



	head.flags  = create.flags;

	head.count  = 1;

	list.memfd  = create.memfd;

	list.offset = create.offset;

	list.size   = create.size;



	return udmabuf_create(&head, &list);

}



static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)

{

	struct udmabuf_create_list head;

	struct udmabuf_create_item *list;

	int ret = -EINVAL;

	u32 lsize;



	if (copy_from_user(&head, (void __user *)arg, sizeof(head)))

		return -EFAULT;

	if (head.count > 1024)

		return -EINVAL;

	lsize = sizeof(struct udmabuf_create_item) * head.count;

	list = memdup_user((void __user *)(arg + sizeof(head)), lsize);

	if (IS_ERR(list))

		return PTR_ERR(list);



	ret = udmabuf_create(&head, list);

	kfree(list);

	return ret;

}



static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,

			  unsigned long arg)

{

	long ret;



	switch (ioctl) {

	case UDMABUF_CREATE:

		ret = udmabuf_ioctl_create(filp, arg);

		break;

	case UDMABUF_CREATE_LIST:

		ret = udmabuf_ioctl_create_list(filp, arg);

		break;

	default:

		ret = -EINVAL;

		break;

	}

	return ret;

}



static const struct file_operations udmabuf_fops = {

	.owner		= THIS_MODULE,

	.unlocked_ioctl = udmabuf_ioctl,

};



static struct miscdevice udmabuf_misc = {

	.minor          = MISC_DYNAMIC_MINOR,

	.name           = "udmabuf",

	.fops           = &udmabuf_fops,

};



static int __init udmabuf_dev_init(void)

{

	return misc_register(&udmabuf_misc);

}



static void __exit udmabuf_dev_exit(void)

{

	misc_deregister(&udmabuf_misc);

}



module_init(udmabuf_dev_init)

module_exit(udmabuf_dev_exit)



MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");

MODULE_LICENSE("GPL v2");