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iommu: Introduce a new iommu_group_replace_domain() API

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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: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Nicolin Chen 2023-07-17 15:12:09 -03:00 • committed by Jason Gunthorpe
parent ea2d6124b5
commit addb665924
2 changed files with 37 additions and 0 deletions
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10
drivers/iommu/iommu-priv.h Normal file
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@ -0,0 +1,10 @@
/* 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 */

27
drivers/iommu/iommu.c
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@ -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,