Commit addb6659 authored by Nicolin Chen's avatar Nicolin Chen Committed by Jason Gunthorpe
Browse files

iommu: Introduce a new iommu_group_replace_domain() API 

qemu has a need to replace the translations associated with a domain
when the guest does large-scale operations like switching between an
IDENTITY domain and, say, dma-iommu.c.

Currently, it does this by replacing all the mappings in a single
domain, but this is very inefficient and means that domains have to be
per-device rather than per-translation.

Provide a high-level API to allow replacements of one domain with
another. This is similar to a detach/attach cycle except it doesn't
force the group to go to the blocking domain in-between.

By removing this forced blocking domain the iommu driver has the
opportunity to implement a non-disruptive replacement of the domain to the
greatest extent its hardware allows. This allows the qemu emulation of the
vIOMMU to be more complete, as real hardware often has a non-distruptive
replacement capability.

It could be possible to address this by simply removing the protection
from the iommu_attach_group(), but it is not so clear if that is safe for
the few users. Thus, add a new API to serve this new purpose.

All drivers are already required to support changing between active
UNMANAGED domains when using their attach_dev ops.

This API is expected to be used only by IOMMUFD, so add to the iommu-priv
header and mark it as IOMMUFD_INTERNAL.

Link: https://lore.kernel.org/r/13-v8-6659224517ea+532-iommufd_alloc_jgg@nvidia.com


Suggested-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent ea2d6124

drivers/iommu/iommu-priv.h

0 → 100644
+10 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */

#ifndef __LINUX_IOMMU_PRIV_H

#define __LINUX_IOMMU_PRIV_H



#include <linux/iommu.h>



int iommu_group_replace_domain(struct iommu_group *group,

			       struct iommu_domain *new_domain);



#endif /* __LINUX_IOMMU_PRIV_H */

drivers/iommu/iommu.c

+27 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/msi.h>



#include "dma-iommu.h"

#include "iommu-priv.h"



#include "iommu-sva.h"
@@ -2114,6 +2115,32 @@ int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group) 
}

EXPORT_SYMBOL_GPL(iommu_attach_group);



/**

 * iommu_group_replace_domain - replace the domain that a group is attached to

 * @new_domain: new IOMMU domain to replace with

 * @group: IOMMU group that will be attached to the new domain

 *

 * This API allows the group to switch domains without being forced to go to

 * the blocking domain in-between.

 *

 * If the currently attached domain is a core domain (e.g. a default_domain),

 * it will act just like the iommu_attach_group().

 */

int iommu_group_replace_domain(struct iommu_group *group,

			       struct iommu_domain *new_domain)

{

	int ret;



	if (!new_domain)

		return -EINVAL;



	mutex_lock(&group->mutex);

	ret = __iommu_group_set_domain(group, new_domain);

	mutex_unlock(&group->mutex);

	return ret;

}

EXPORT_SYMBOL_NS_GPL(iommu_group_replace_domain, IOMMUFD_INTERNAL);



static int __iommu_device_set_domain(struct iommu_group *group,

				     struct device *dev,

				     struct iommu_domain *new_domain,