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iommu: iommu_group_claim_dma_owner() must always assign a domain

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Once the group enters 'owned' mode it can never be assigned back to the
default_domain or to a NULL domain. It must always be actively assigned to
a current domain. If the caller hasn't provided a domain then the core
must provide an explicit DMA blocking domain that has no DMA map.

Lazily create a group-global blocking DMA domain when
iommu_group_claim_dma_owner is first called and immediately assign the
group to it. This ensures that DMA is immediately fully isolated on all
IOMMU drivers.

If the user attaches/detaches while owned then detach will set the group
back to the blocking domain.

Slightly reorganize the call chains so that
__iommu_group_set_core_domain() is the function that removes any caller
configured domain and sets the domains back a core owned domain with an
appropriate lifetime.

__iommu_group_set_domain() is the worker function that can change the
domain assigned to a group to any target domain, including NULL.

Add comments clarifying how the NULL vs detach_dev vs default_domain works
based on Robin's remarks.

This fixes an oops with VFIO and SMMUv3 because VFIO will call
iommu_detach_group() and then immediately iommu_domain_free(), but
SMMUv3 has no way to know that the domain it is holding a pointer to
has been freed. Now the iommu_detach_group() will assign the blocking
domain and SMMUv3 will no longer hold a stale domain reference.

Fixes: 1ea2a07a53 ("iommu: Add DMA ownership management interfaces")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Tested-by: Baolu Lu <baolu.lu@linux.intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Co-developed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
--

Just minor polishing as discussed

v3:
 - Change names to __iommu_group_set_domain() /
   __iommu_group_set_core_domain()
 - Clarify comments
 - Call __iommu_group_set_domain() directly in
   iommu_group_release_dma_owner() since we know it is always selecting
   the default_domain
 - Remove redundant detach_dev ops check in __iommu_detach_device and
   make the added WARN_ON fail instead
 - Check for blocking_domain in __iommu_attach_group() so VFIO can
   actually attach a new group
 - Update comments and spelling
 - Fix missed change to new_domain in iommu_group_do_detach_device()

v2: https://lore.kernel.org/r/0-v2-f62259511ac0+6-iommu_dma_block_jgg@nvidia.com
v1: https://lore.kernel.org/r/0-v1-6e9d2d0a759d+11b-iommu_dma_block_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/0-v3-db7f0785022b+149-iommu_dma_block_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Jason Gunthorpe via iommu 2022-05-09 13:19:19 -03:00 committed by Joerg Roedel
parent a5f1bd1afa
commit 0286300e60
1 changed files with 91 additions and 36 deletions
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127
drivers/iommu/iommu.c
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@ -44,6 +44,7 @@ struct iommu_group {
char *name;
int id;
struct iommu_domain *default_domain;
struct iommu_domain *blocking_domain;
struct iommu_domain *domain;
struct list_head entry;
unsigned int owner_cnt;
@ -82,8 +83,8 @@ static int __iommu_attach_device(struct iommu_domain *domain,
struct device *dev);
static int __iommu_attach_group(struct iommu_domain *domain,
struct iommu_group *group);
static void __iommu_detach_group(struct iommu_domain *domain,
struct iommu_group *group);
static int __iommu_group_set_domain(struct iommu_group *group,
struct iommu_domain *new_domain);
static int iommu_create_device_direct_mappings(struct iommu_group *group,
struct device *dev);
static struct iommu_group *iommu_group_get_for_dev(struct device *dev);
@ -596,6 +597,8 @@ static void iommu_group_release(struct kobject *kobj)
if (group->default_domain)
iommu_domain_free(group->default_domain);
if (group->blocking_domain)
iommu_domain_free(group->blocking_domain);
kfree(group->name);
kfree(group);
@ -1907,6 +1910,24 @@ void iommu_domain_free(struct iommu_domain *domain)
}
EXPORT_SYMBOL_GPL(iommu_domain_free);
/*
* Put the group's domain back to the appropriate core-owned domain - either the
* standard kernel-mode DMA configuration or an all-DMA-blocked domain.
*/
static void __iommu_group_set_core_domain(struct iommu_group *group)
{
struct iommu_domain *new_domain;
int ret;
if (group->owner)
new_domain = group->blocking_domain;
else
new_domain = group->default_domain;
ret = __iommu_group_set_domain(group, new_domain);
WARN(ret, "iommu driver failed to attach the default/blocking domain");
}
static int __iommu_attach_device(struct iommu_domain *domain,
struct device *dev)
{
@ -1963,9 +1984,6 @@ static void __iommu_detach_device(struct iommu_domain *domain,
if (iommu_is_attach_deferred(dev))
return;
if (unlikely(domain->ops->detach_dev == NULL))
return;
domain->ops->detach_dev(domain, dev);
trace_detach_device_from_domain(dev);
}
@ -1979,12 +1997,10 @@ void iommu_detach_device(struct iommu_domain *domain, struct device *dev)
return;
mutex_lock(&group->mutex);
if (iommu_group_device_count(group) != 1) {
WARN_ON(1);
if (WARN_ON(domain != group->domain) ||
WARN_ON(iommu_group_device_count(group) != 1))
goto out_unlock;
}
__iommu_detach_group(domain, group);
__iommu_group_set_core_domain(group);
out_unlock:
mutex_unlock(&group->mutex);
@ -2040,7 +2056,8 @@ static int __iommu_attach_group(struct iommu_domain *domain,
{
int ret;
if (group->domain && group->domain != group->default_domain)
if (group->domain && group->domain != group->default_domain &&
group->domain != group->blocking_domain)
return -EBUSY;
ret = __iommu_group_for_each_dev(group, domain,
@ -2072,38 +2089,49 @@ static int iommu_group_do_detach_device(struct device *dev, void *data)
return 0;
}
static void __iommu_detach_group(struct iommu_domain *domain,
struct iommu_group *group)
static int __iommu_group_set_domain(struct iommu_group *group,
struct iommu_domain *new_domain)
{
int ret;
if (group->domain == new_domain)
return 0;
/*
* If the group has been claimed already, do not re-attach the default
* domain.
* New drivers should support default domains and so the detach_dev() op
* will never be called. Otherwise the NULL domain represents some
* platform specific behavior.
*/
if (!group->default_domain || group->owner) {
__iommu_group_for_each_dev(group, domain,
if (!new_domain) {
if (WARN_ON(!group->domain->ops->detach_dev))
return -EINVAL;
__iommu_group_for_each_dev(group, group->domain,
iommu_group_do_detach_device);
group->domain = NULL;
return;
return 0;
}
if (group->domain == group->default_domain)
return;
/* Detach by re-attaching to the default domain */
ret = __iommu_group_for_each_dev(group, group->default_domain,
/*
* Changing the domain is done by calling attach_dev() on the new
* domain. This switch does not have to be atomic and DMA can be
* discarded during the transition. DMA must only be able to access
* either new_domain or group->domain, never something else.
*
* Note that this is called in error unwind paths, attaching to a
* domain that has already been attached cannot fail.
*/
ret = __iommu_group_for_each_dev(group, new_domain,
iommu_group_do_attach_device);
if (ret != 0)
WARN_ON(1);
else
group->domain = group->default_domain;
if (ret)
return ret;
group->domain = new_domain;
return 0;
}
void iommu_detach_group(struct iommu_domain *domain, struct iommu_group *group)
{
mutex_lock(&group->mutex);
__iommu_detach_group(domain, group);
__iommu_group_set_core_domain(group);
mutex_unlock(&group->mutex);
}
EXPORT_SYMBOL_GPL(iommu_detach_group);
@ -3088,6 +3116,29 @@ void iommu_device_unuse_default_domain(struct device *dev)
iommu_group_put(group);
}
static int __iommu_group_alloc_blocking_domain(struct iommu_group *group)
{
struct group_device *dev =
list_first_entry(&group->devices, struct group_device, list);
if (group->blocking_domain)
return 0;
group->blocking_domain =
__iommu_domain_alloc(dev->dev->bus, IOMMU_DOMAIN_BLOCKED);
if (!group->blocking_domain) {
/*
* For drivers that do not yet understand IOMMU_DOMAIN_BLOCKED
* create an empty domain instead.
*/
group->blocking_domain = __iommu_domain_alloc(
dev->dev->bus, IOMMU_DOMAIN_UNMANAGED);
if (!group->blocking_domain)
return -EINVAL;
}
return 0;
}
/**
* iommu_group_claim_dma_owner() - Set DMA ownership of a group
* @group: The group.
@ -3111,9 +3162,14 @@ int iommu_group_claim_dma_owner(struct iommu_group *group, void *owner)
goto unlock_out;
}
ret = __iommu_group_alloc_blocking_domain(group);
if (ret)
goto unlock_out;
ret = __iommu_group_set_domain(group, group->blocking_domain);
if (ret)
goto unlock_out;
group->owner = owner;
if (group->domain)
__iommu_detach_group(group->domain, group);
}
group->owner_cnt++;
@ -3132,18 +3188,17 @@ EXPORT_SYMBOL_GPL(iommu_group_claim_dma_owner);
*/
void iommu_group_release_dma_owner(struct iommu_group *group)
{
int ret;
mutex_lock(&group->mutex);
if (WARN_ON(!group->owner_cnt || !group->owner))
goto unlock_out;
group->owner_cnt = 0;
/*
* The UNMANAGED domain should be detached before all USER
* owners have been released.
*/
if (!WARN_ON(group->domain) && group->default_domain)
__iommu_attach_group(group->default_domain, group);
group->owner = NULL;
ret = __iommu_group_set_domain(group, group->default_domain);
WARN(ret, "iommu driver failed to attach the default domain");
unlock_out:
mutex_unlock(&group->mutex);
}