Commit 01f70cbb authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

iommufd: Allow iommufd to supply /dev/vfio/vfio 

If the VFIO container is compiled out, give a kconfig option for iommufd
to provide the miscdev node with the same name and permissions as vfio
uses.

The compatibility node supports the same ioctls as VFIO and automatically
enables the VFIO compatible pinned page accounting mode.

Link: https://lore.kernel.org/r/10-v4-42cd2eb0e3eb+335a-vfio_iommufd_jgg@nvidia.com


Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarYi Liu <yi.l.liu@intel.com>
Reviewed-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Tested-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Tested-by: default avatarYi Liu <yi.l.liu@intel.com>
Tested-by: default avatarLixiao Yang <lixiao.yang@intel.com>
Tested-by: default avatarMatthew Rosato <mjrosato@linux.ibm.com>
Tested-by: default avatarYu He <yu.he@intel.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent e5a9ec7e

drivers/iommu/iommufd/Kconfig

+20 −0
Original line number Diff line number Diff line
@@ -12,6 +12,26 @@ config IOMMUFD 
	  If you don't know what to do here, say N.



if IOMMUFD

config IOMMUFD_VFIO_CONTAINER

	bool "IOMMUFD provides the VFIO container /dev/vfio/vfio"

	depends on VFIO && !VFIO_CONTAINER

	default VFIO && !VFIO_CONTAINER

	help

	  IOMMUFD will provide /dev/vfio/vfio instead of VFIO. This relies on

	  IOMMUFD providing compatibility emulation to give the same ioctls.

	  It provides an option to build a kernel with legacy VFIO components

	  removed.



	  IOMMUFD VFIO container emulation is known to lack certain features

	  of the native VFIO container, such as no-IOMMU support, peer-to-peer

	  DMA mapping, PPC IOMMU support, as well as other potentially

	  undiscovered gaps.  This option is currently intended for the

	  purpose of testing IOMMUFD with unmodified userspace supporting VFIO

	  and making use of the Type1 VFIO IOMMU backend.  General purpose

	  enabling of this option is currently discouraged.



	  Unless testing IOMMUFD, say N here.



config IOMMUFD_TEST

	bool "IOMMU Userspace API Test support"

	depends on DEBUG_KERNEL

drivers/iommu/iommufd/main.c

+36 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <uapi/linux/iommufd.h>

#include <linux/iommufd.h>



#include "io_pagetable.h"

#include "iommufd_private.h"

#include "iommufd_test.h"
@@ -25,6 +26,7 @@ struct iommufd_object_ops { 
	void (*destroy)(struct iommufd_object *obj);

};

static const struct iommufd_object_ops iommufd_object_ops[];

static struct miscdevice vfio_misc_dev;



struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,

					     size_t size,
@@ -170,6 +172,16 @@ static int iommufd_fops_open(struct inode *inode, struct file *filp) 
	if (!ictx)

		return -ENOMEM;



	/*

	 * For compatibility with VFIO when /dev/vfio/vfio is opened we default

	 * to the same rlimit accounting as vfio uses.

	 */

	if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER) &&

	    filp->private_data == &vfio_misc_dev) {

		ictx->account_mode = IOPT_PAGES_ACCOUNT_MM;

		pr_info_once("IOMMUFD is providing /dev/vfio/vfio, not VFIO.\n");

	}



	xa_init_flags(&ictx->objects, XA_FLAGS_ALLOC1 | XA_FLAGS_ACCOUNT);

	ictx->file = filp;

	filp->private_data = ictx;
@@ -400,6 +412,15 @@ static struct miscdevice iommu_misc_dev = { 
	.mode = 0660,

};





static struct miscdevice vfio_misc_dev = {

	.minor = VFIO_MINOR,

	.name = "vfio",

	.fops = &iommufd_fops,

	.nodename = "vfio/vfio",

	.mode = 0666,

};



static int __init iommufd_init(void)

{

	int ret;
@@ -407,18 +428,33 @@ static int __init iommufd_init(void) 
	ret = misc_register(&iommu_misc_dev);

	if (ret)

		return ret;



	if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER)) {

		ret = misc_register(&vfio_misc_dev);

		if (ret)

			goto err_misc;

	}

	iommufd_test_init();

	return 0;

err_misc:

	misc_deregister(&iommu_misc_dev);

	return ret;

}



static void __exit iommufd_exit(void)

{

	iommufd_test_exit();

	if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER))

		misc_deregister(&vfio_misc_dev);

	misc_deregister(&iommu_misc_dev);

}



module_init(iommufd_init);

module_exit(iommufd_exit);



#if IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER)

MODULE_ALIAS_MISCDEV(VFIO_MINOR);

MODULE_ALIAS("devname:vfio/vfio");

#endif

MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");

MODULE_LICENSE("GPL");