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iommu: Replace device_lock() with group->mutex

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device_lock() was used in iommu_group_store_type() to prevent the
devices in an iommu group from being attached by any device driver.
On the other hand, in order to avoid lock race between group->mutex
and device_lock(), it limited the usage scenario to the singleton
groups.

We already have the DMA ownership scheme to avoid driver attachment
and group->mutex ensures that device ops are always valid, there's
no need for device_lock() anymore. Remove device_lock() and the
singleton group limitation.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20230322064956.263419-6-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Lu Baolu 2023-03-22 14:49:55 +08:00 committed by Joerg Roedel
parent 33793748de
commit 49a22aae7d
1 changed files with 18 additions and 63 deletions
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81
drivers/iommu/iommu.c
View file

@ -2956,14 +2956,6 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
goto out;
}
/* We can bring up a flush queue without tearing down the domain */
if (type == IOMMU_DOMAIN_DMA_FQ && prev_dom->type == IOMMU_DOMAIN_DMA) {
ret = iommu_dma_init_fq(prev_dom);
if (!ret)
prev_dom->type = IOMMU_DOMAIN_DMA_FQ;
goto out;
}
/* Sets group->default_domain to the newly allocated domain */
ret = iommu_group_alloc_default_domain(dev->bus, group, type);
if (ret)
@ -2996,7 +2988,7 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
* transition. Return failure if this isn't met.
*
* We need to consider the race between this and the device release path.
* device_lock(dev) is used here to guarantee that the device release path
* group->mutex is used here to guarantee that the device release path
* will not be entered at the same time.
*/
static ssize_t iommu_group_store_type(struct iommu_group *group,
@ -3023,61 +3015,29 @@ static ssize_t iommu_group_store_type(struct iommu_group *group,
else
return -EINVAL;
/*
* Lock/Unlock the group mutex here before device lock to
* 1. Make sure that the iommu group has only one device (this is a
* prerequisite for step 2)
* 2. Get struct *dev which is needed to lock device
*/
mutex_lock(&group->mutex);
if (iommu_group_device_count(group) != 1) {
/* We can bring up a flush queue without tearing down the domain. */
if (req_type == IOMMU_DOMAIN_DMA_FQ &&
group->default_domain->type == IOMMU_DOMAIN_DMA) {
ret = iommu_dma_init_fq(group->default_domain);
if (!ret)
group->default_domain->type = IOMMU_DOMAIN_DMA_FQ;
mutex_unlock(&group->mutex);
pr_err_ratelimited("Cannot change default domain: Group has more than one device\n");
return -EINVAL;
return ret ?: count;
}
/* Otherwise, ensure that device exists and no driver is bound. */
if (list_empty(&group->devices) || group->owner_cnt) {
mutex_unlock(&group->mutex);
return -EPERM;
}
/* Since group has only one device */
grp_dev = list_first_entry(&group->devices, struct group_device, list);
dev = grp_dev->dev;
get_device(dev);
/*
* Don't hold the group mutex because taking group mutex first and then
* the device lock could potentially cause a deadlock as below. Assume
* two threads T1 and T2. T1 is trying to change default domain of an
* iommu group and T2 is trying to hot unplug a device or release [1] VF
* of a PCIe device which is in the same iommu group. T1 takes group
* mutex and before it could take device lock assume T2 has taken device
* lock and is yet to take group mutex. Now, both the threads will be
* waiting for the other thread to release lock. Below, lock order was
* suggested.
* device_lock(dev);
* mutex_lock(&group->mutex);
* iommu_change_dev_def_domain();
* mutex_unlock(&group->mutex);
* device_unlock(dev);
*
* [1] Typical device release path
* device_lock() from device/driver core code
* -> bus_notifier()
* -> iommu_bus_notifier()
* -> iommu_release_device()
* -> ops->release_device() vendor driver calls back iommu core code
* -> mutex_lock() from iommu core code
*/
mutex_unlock(&group->mutex);
/* Check if the device in the group still has a driver bound to it */
device_lock(dev);
if (device_is_bound(dev) && !(req_type == IOMMU_DOMAIN_DMA_FQ &&
group->default_domain->type == IOMMU_DOMAIN_DMA)) {
pr_err_ratelimited("Device is still bound to driver\n");
ret = -EBUSY;
goto out;
}
mutex_lock(&group->mutex);
ret = iommu_change_dev_def_domain(group, dev, req_type);
/*
* Release the mutex here because ops->probe_finalize() call-back of
* some vendor IOMMU drivers calls arm_iommu_attach_device() which
@ -3088,14 +3048,9 @@ static ssize_t iommu_group_store_type(struct iommu_group *group,
/* Make sure dma_ops is appropriatley set */
if (!ret)
iommu_group_do_probe_finalize(dev, group->default_domain);
ret = ret ?: count;
__iommu_group_dma_finalize(group);
out:
device_unlock(dev);
put_device(dev);
return ret;
return ret ?: count;
}
static bool iommu_is_default_domain(struct iommu_group *group)