Re: [PATCH v2 3/9] iommu/ioasid: Introduce ioasid_set APIs

[Jacob Pan]

On Mon, 24 Aug 2020 10:24:11 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> Hi Jacob,
> 
> On 8/22/20 12:35 PM, Jacob Pan wrote:
> > ioasid_set was introduced as an arbitrary token that are shared by a
> > group of IOASIDs. For example, if IOASID #1 and #2 are allocated
> > via the same ioasid_set*, they are viewed as to belong to the same
> > set.
> > 
> > For guest SVA usages, system-wide IOASID resources need to be
> > partitioned such that VMs can have its own quota and being managed
> > separately. ioasid_set is the perfect candidate for meeting such
> > requirements. This patch redefines and extends ioasid_set with the
> > following new fields:
> > - Quota
> > - Reference count
> > - Storage of its namespace
> > - The token is stored in the new ioasid_set but with optional types
> > 
> > ioasid_set level APIs are introduced that wires up these new data.
> > Existing users of IOASID APIs are converted where a host IOASID set
> > is allocated for bare-metal usage.
> > 
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.c |  27 ++-
> >   drivers/iommu/intel/pasid.h |   1 +
> >   drivers/iommu/intel/svm.c   |   8 +-
> >   drivers/iommu/ioasid.c      | 390
> > +++++++++++++++++++++++++++++++++++++++++---
> > include/linux/ioasid.h      |  82 ++++++++-- 5 files changed, 465
> > insertions(+), 43 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel/iommu.c
> > b/drivers/iommu/intel/iommu.c index a3a0b5c8921d..5813eeaa5edb
> > 100644 --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -42,6 +42,7 @@
> >   #include <linux/crash_dump.h>
> >   #include <linux/numa.h>
> >   #include <linux/swiotlb.h>
> > +#include <linux/ioasid.h>
> >   #include <asm/irq_remapping.h>
> >   #include <asm/cacheflush.h>
> >   #include <asm/iommu.h>
> > @@ -103,6 +104,9 @@
> >    */
> >   #define INTEL_IOMMU_PGSIZES	(~0xFFFUL)
> >   
> > +/* PASIDs used by host SVM */
> > +struct ioasid_set *host_pasid_set;
> > +
> >   static inline int agaw_to_level(int agaw)
> >   {
> >   	return agaw + 2;
> > @@ -3103,8 +3107,8 @@ static void intel_vcmd_ioasid_free(ioasid_t
> > ioasid, void *data)
> >   	 * Sanity check the ioasid owner is done at upper layer,
> > e.g. VFIO
> >   	 * We can only free the PASID when all the devices are
> > unbound. */
> > -	if (ioasid_find(NULL, ioasid, NULL)) {
> > -		pr_alert("Cannot free active IOASID %d\n", ioasid);
> > +	if (IS_ERR(ioasid_find(host_pasid_set, ioasid, NULL))) {
> > +		pr_err("Cannot free IOASID %d, not in system
> > set\n", ioasid); return;
> >   	}
> >   	vcmd_free_pasid(iommu, ioasid);
> > @@ -3288,6 +3292,19 @@ static int __init init_dmars(void)
> >   	if (ret)
> >   		goto free_iommu;
> >   
> > +	/* PASID is needed for scalable mode irrespective to SVM */
> > +	if (intel_iommu_sm) {
> > +		ioasid_install_capacity(intel_pasid_max_id);
> > +		/* We should not run out of IOASIDs at boot */
> > +		host_pasid_set = ioasid_alloc_set(NULL,
> > PID_MAX_DEFAULT,
> > +
> > IOASID_SET_TYPE_NULL);
> > +		if (IS_ERR_OR_NULL(host_pasid_set)) {
> > +			pr_err("Failed to enable host PASID
> > allocator %lu\n",
> > +				PTR_ERR(host_pasid_set));
> > +			intel_iommu_sm = 0;
> > +		}
> > +	}
> > +
> >   	/*
> >   	 * for each drhd
> >   	 *   enable fault log
> > @@ -5149,7 +5166,7 @@ static void auxiliary_unlink_device(struct
> > dmar_domain *domain, domain->auxd_refcnt--;
> >   
> >   	if (!domain->auxd_refcnt && domain->default_pasid > 0)
> > -		ioasid_free(domain->default_pasid);
> > +		ioasid_free(host_pasid_set, domain->default_pasid);
> >   }
> >   
> >   static int aux_domain_add_dev(struct dmar_domain *domain,
> > @@ -5167,7 +5184,7 @@ static int aux_domain_add_dev(struct
> > dmar_domain *domain, int pasid;
> >   
> >   		/* No private data needed for the default pasid */
> > -		pasid = ioasid_alloc(NULL, PASID_MIN,
> > +		pasid = ioasid_alloc(host_pasid_set, PASID_MIN,
> >   				     pci_max_pasids(to_pci_dev(dev))
> > - 1, NULL);
> >   		if (pasid == INVALID_IOASID) {
> > @@ -5210,7 +5227,7 @@ static int aux_domain_add_dev(struct
> > dmar_domain *domain, spin_unlock(&iommu->lock);
> >   	spin_unlock_irqrestore(&device_domain_lock, flags);
> >   	if (!domain->auxd_refcnt && domain->default_pasid > 0)
> > -		ioasid_free(domain->default_pasid);
> > +		ioasid_free(host_pasid_set, domain->default_pasid);
> >   
> >   	return ret;
> >   }
> > diff --git a/drivers/iommu/intel/pasid.h
> > b/drivers/iommu/intel/pasid.h index c9850766c3a9..ccdc23446015
> > 100644 --- a/drivers/iommu/intel/pasid.h
> > +++ b/drivers/iommu/intel/pasid.h
> > @@ -99,6 +99,7 @@ static inline bool pasid_pte_is_present(struct
> > pasid_entry *pte) }
> >   
> >   extern u32 intel_pasid_max_id;
> > +extern struct ioasid_set *host_pasid_set;
> >   int intel_pasid_alloc_id(void *ptr, int start, int end, gfp_t
> > gfp); void intel_pasid_free_id(int pasid);
> >   void *intel_pasid_lookup_id(int pasid);
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index 37a9beabc0ca..634e191ca2c3 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -551,7 +551,7 @@ intel_svm_bind_mm(struct device *dev, int
> > flags, struct svm_dev_ops *ops, pasid_max = intel_pasid_max_id;
> >   
> >   		/* Do not use PASID 0, reserved for RID to PASID
> > */
> > -		svm->pasid = ioasid_alloc(NULL, PASID_MIN,
> > +		svm->pasid = ioasid_alloc(host_pasid_set,
> > PASID_MIN, pasid_max - 1, svm);
> >   		if (svm->pasid == INVALID_IOASID) {
> >   			kfree(svm);
> > @@ -568,7 +568,7 @@ intel_svm_bind_mm(struct device *dev, int
> > flags, struct svm_dev_ops *ops, if (mm) {
> >   			ret =
> > mmu_notifier_register(&svm->notifier, mm); if (ret) {
> > -				ioasid_free(svm->pasid);
> > +				ioasid_free(host_pasid_set,
> > svm->pasid); kfree(svm);
> >   				kfree(sdev);
> >   				goto out;
> > @@ -586,7 +586,7 @@ intel_svm_bind_mm(struct device *dev, int
> > flags, struct svm_dev_ops *ops, if (ret) {
> >   			if (mm)
> >   				mmu_notifier_unregister(&svm->notifier,
> > mm);
> > -			ioasid_free(svm->pasid);
> > +			ioasid_free(host_pasid_set, svm->pasid);
> >   			kfree(svm);
> >   			kfree(sdev);
> >   			goto out;
> > @@ -655,7 +655,7 @@ static int intel_svm_unbind_mm(struct device
> > *dev, int pasid) kfree_rcu(sdev, rcu);
> >   
> >   			if (list_empty(&svm->devs)) {
> > -				ioasid_free(svm->pasid);
> > +				ioasid_free(host_pasid_set,
> > svm->pasid); if (svm->mm)
> >   					mmu_notifier_unregister(&svm->notifier,
> > svm->mm); list_del(&svm->list);
> > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> > index 5f63af07acd5..f73b3dbfc37a 100644
> > --- a/drivers/iommu/ioasid.c
> > +++ b/drivers/iommu/ioasid.c
> > @@ -1,22 +1,58 @@
> >   // SPDX-License-Identifier: GPL-2.0
> >   /*
> >    * I/O Address Space ID allocator. There is one global IOASID
> > space, split into
> > - * subsets. Users create a subset with DECLARE_IOASID_SET, then
> > allocate and
> > - * free IOASIDs with ioasid_alloc and ioasid_free.
> > + * subsets. Users create a subset with ioasid_alloc_set, then
> > allocate/free IDs
> > + * with ioasid_alloc and ioasid_free.
> >    */
> > -#include <linux/ioasid.h>
> >   #include <linux/module.h>
> >   #include <linux/slab.h>
> >   #include <linux/spinlock.h>
> >   #include <linux/xarray.h>
> > +#include <linux/ioasid.h>
> > +
> > +static DEFINE_XARRAY_ALLOC(ioasid_sets);
> > +enum ioasid_state {
> > +	IOASID_STATE_INACTIVE,
> > +	IOASID_STATE_ACTIVE,
> > +	IOASID_STATE_FREE_PENDING,
> > +};
> >   
> > +/**
> > + * struct ioasid_data - Meta data about ioasid
> > + *
> > + * @id:		Unique ID
> > + * @users	Number of active users
> > + * @state	Track state of the IOASID
> > + * @set		Meta data of the set this IOASID belongs to
> > + * @private	Private data associated with the IOASID
> > + * @rcu		For free after RCU grace period
> > + */
> >   struct ioasid_data {
> >   	ioasid_t id;
> >   	struct ioasid_set *set;
> > +	refcount_t users;
> > +	enum ioasid_state state;
> >   	void *private;
> >   	struct rcu_head rcu;
> >   };
> >   
> > +/* Default to PCIe standard 20 bit PASID */
> > +#define PCI_PASID_MAX 0x100000
> > +static ioasid_t ioasid_capacity = PCI_PASID_MAX;
> > +static ioasid_t ioasid_capacity_avail = PCI_PASID_MAX;
> > +
> > +void ioasid_install_capacity(ioasid_t total)
> > +{
> > +	ioasid_capacity = ioasid_capacity_avail = total;  
> 
> Need any check for multiple settings or setting after used?
> 
Good point, capacity can only be set once. will add check to prevent
setting after use.

> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_install_capacity);
> > +
> > +ioasid_t ioasid_get_capacity()
> > +{
> > +	return ioasid_capacity;
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_get_capacity);
> > +
> >   /*
> >    * struct ioasid_allocator_data - Internal data structure to hold
> > information
> >    * about an allocator. There are two types of allocators:
> > @@ -306,11 +342,23 @@ ioasid_t ioasid_alloc(struct ioasid_set *set,
> > ioasid_t min, ioasid_t max, {
> >   	struct ioasid_data *data;
> >   	void *adata;
> > -	ioasid_t id;
> > +	ioasid_t id = INVALID_IOASID;
> > +
> > +	spin_lock(&ioasid_allocator_lock);
> > +	/* Check if the IOASID set has been allocated and
> > initialized */
> > +	if (WARN_ON(xa_load(&ioasid_sets, set->sid) != set)) {
> > +		pr_warn("Invalid set\n");
> > +		goto done_unlock;
> > +	}
> > +
> > +	if (set->quota <= set->nr_ioasids) {
> > +		pr_err("IOASID set %d out of quota %d\n",
> > set->sid, set->quota);
> > +		goto done_unlock;
> > +	}
> >   
> >   	data = kzalloc(sizeof(*data), GFP_ATOMIC);
> >   	if (!data)
> > -		return INVALID_IOASID;
> > +		goto done_unlock;
> >   
> >   	data->set = set;
> >   	data->private = private;
> > @@ -319,7 +367,6 @@ ioasid_t ioasid_alloc(struct ioasid_set *set,
> > ioasid_t min, ioasid_t max,
> >   	 * Custom allocator needs allocator data to perform
> > platform specific
> >   	 * operations.
> >   	 */
> > -	spin_lock(&ioasid_allocator_lock);
> >   	adata = active_allocator->flags &
> > IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data; id =
> > active_allocator->ops->alloc(min, max, adata); if (id ==
> > INVALID_IOASID) { @@ -335,42 +382,339 @@ ioasid_t
> > ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
> > goto exit_free; }
> >   	data->id = id;
> > +	data->state = IOASID_STATE_ACTIVE;
> > +	refcount_set(&data->users, 1);
> > +
> > +	/* Store IOASID in the per set data */
> > +	if (xa_err(xa_store(&set->xa, id, data, GFP_ATOMIC))) {
> > +		pr_err("Failed to ioasid %d in set %d\n", id,
> > set->sid);
> > +		goto exit_free;
> > +	}
> > +	set->nr_ioasids++;
> > +	goto done_unlock;
> >   
> > -	spin_unlock(&ioasid_allocator_lock);
> > -	return id;
> >   exit_free:
> > -	spin_unlock(&ioasid_allocator_lock);
> >   	kfree(data);
> > -	return INVALID_IOASID;
> > +done_unlock:
> > +	spin_unlock(&ioasid_allocator_lock);
> > +	return id;
> >   }
> >   EXPORT_SYMBOL_GPL(ioasid_alloc);
> >   
> > +static void ioasid_do_free(struct ioasid_data *data)
> > +{
> > +	struct ioasid_data *ioasid_data;
> > +	struct ioasid_set *sdata;
> > +
> > +	active_allocator->ops->free(data->id,
> > active_allocator->ops->pdata);
> > +	/* Custom allocator needs additional steps to free the xa
> > element */
> > +	if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
> > +		ioasid_data = xa_erase(&active_allocator->xa,
> > data->id);
> > +		kfree_rcu(ioasid_data, rcu);
> > +	}
> > +
> > +	sdata = xa_load(&ioasid_sets, data->set->sid);
> > +	if (!sdata) {
> > +		pr_err("No set %d for IOASID %d\n", data->set->sid,
> > +		       data->id);
> > +		return;
> > +	}
> > +	xa_erase(&sdata->xa, data->id);
> > +	sdata->nr_ioasids--;
> > +}
> > +
> > +static void ioasid_free_locked(struct ioasid_set *set, ioasid_t
> > ioasid) +{
> > +	struct ioasid_data *data;
> > +
> > +	data = xa_load(&active_allocator->xa, ioasid);
> > +	if (!data) {
> > +		pr_err("Trying to free unknown IOASID %u\n",
> > ioasid);
> > +		return;
> > +	}
> > +
> > +	if (data->set != set) {
> > +		pr_warn("Cannot free IOASID %u due to set
> > ownership\n", ioasid);
> > +		return;
> > +	}
> > +	data->state = IOASID_STATE_FREE_PENDING;
> > +
> > +	if (!refcount_dec_and_test(&data->users))
> > +		return;
> > +
> > +	ioasid_do_free(data);
> > +}
> > +
> >   /**
> > - * ioasid_free - Free an IOASID
> > - * @ioasid: the ID to remove
> > + * ioasid_free - Drop reference on an IOASID. Free if refcount
> > drops to 0,
> > + *               including free from its set and system-wide list.
> > + * @set:	The ioasid_set to check permission with. If not
> > NULL, IOASID
> > + *		free will fail if the set does not match.
> > + * @ioasid:	The IOASID to remove
> >    */
> > -void ioasid_free(ioasid_t ioasid)
> > +void ioasid_free(struct ioasid_set *set, ioasid_t ioasid)
> >   {
> > -	struct ioasid_data *ioasid_data;
> > +	spin_lock(&ioasid_allocator_lock);
> > +	ioasid_free_locked(set, ioasid);
> > +	spin_unlock(&ioasid_allocator_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_free);
> >   
> > +/**
> > + * ioasid_alloc_set - Allocate a new IOASID set for a given token
> > + *
> > + * @token:	Unique token of the IOASID set, cannot be NULL  
> 
> What's the use of @token? I might be able to find the answer in the
> code, but i have no idea when i comes here first time. :-)
> 
You are right, I need to clarify here. How about:
 * @token:	An optional arbitrary number that can be associated
with the
 *		IOASID set. @token can be NULL if the type is
 *		IOASID_SET_TYPE_NULL
 * @quota:	Quota allowed in this set
 * @type:	The type of the token used to create the IOASID set


> This line of comment says that token cannot be NULL. It seems not to
> match the real code, where token could be NULL if type is
> IOASID_SET_TYPE_NULL.
> 
Good catch, it was a relic from previous versions.

> > + * @quota:	Quota allowed in this set. Only for new set
> > creation
> > + * @flags:	Special requirements
> > + *
> > + * IOASID can be limited system-wide resource that requires quota
> > management.
> > + * If caller does not wish to enforce quota, use
> > IOASID_SET_NO_QUOTA flag.  
> 
> If you are not going to add NO_QUOTA support this time, I'd suggest
> you to remove above comment.
> 
Yes, will remove.

> > + *
> > + * Token will be stored in the ioasid_set returned. A reference
> > will be taken
> > + * upon finding a matching set or newly created set.
> > + * IOASID allocation within the set and other per set operations
> > will use
> > + * the retured ioasid_set *.  
> 
> nit: remove *, or you mean the ioasid_set pointer?
> 
Sounds good

> > + *
> > + */
> > +struct ioasid_set *ioasid_alloc_set(void *token, ioasid_t quota,
> > int type) +{
> > +	struct ioasid_set *sdata;
> > +	unsigned long index;
> > +	ioasid_t id;
> > +
> > +	if (type >= IOASID_SET_TYPE_NR)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	/*
> > +	 * Need to check space available if we share system-wide
> > quota.
> > +	 * TODO: we may need to support quota free sets in the
> > future.
> > +	 */
> >   	spin_lock(&ioasid_allocator_lock);
> > -	ioasid_data = xa_load(&active_allocator->xa, ioasid);
> > -	if (!ioasid_data) {
> > -		pr_err("Trying to free unknown IOASID %u\n",
> > ioasid);
> > +	if (quota > ioasid_capacity_avail) {  
> 
> Thinking that ioasid_set itself needs an ioasid, so the check might be
> 
> 	(quota + 1 > ioasid_capacity_avail)?
> 
ioasid_set does not need an ioasid, the set ID is allocated from a
different XArray: ioasid_sets.

> > +		pr_warn("Out of IOASID capacity! ask %d, avail
> > %d\n",
> > +			quota, ioasid_capacity_avail);
> > +		sdata = ERR_PTR(-ENOSPC);
> >   		goto exit_unlock;
> >   	}
> >   
> > -	active_allocator->ops->free(ioasid,
> > active_allocator->ops->pdata);
> > -	/* Custom allocator needs additional steps to free the xa
> > element */
> > -	if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
> > -		ioasid_data = xa_erase(&active_allocator->xa,
> > ioasid);
> > -		kfree_rcu(ioasid_data, rcu);
> > +	/*
> > +	 * Token is only unique within its types but right now we
> > have only
> > +	 * mm type. If we have more token types, we have to match
> > type as well.
> > +	 */
> > +	switch (type) {
> > +	case IOASID_SET_TYPE_MM:
> > +		/* Search existing set tokens, reject duplicates */
> > +		xa_for_each(&ioasid_sets, index, sdata) {
> > +			if (sdata->token == token &&
> > +				sdata->type == IOASID_SET_TYPE_MM)
> > {
> > +				sdata = ERR_PTR(-EEXIST);
> > +				goto exit_unlock;
> > +			}
> > +		}  
> 
> Do you need to enforce non-NULL token policy here?
> 
yes, mm type cannot have NULL token. NULL type must have NULL token.
This design has been flipped a couple of times. Thanks for catching
this.

> > +		break;
> > +	case IOASID_SET_TYPE_NULL:
> > +		if (!token)
> > +			break;
should not be NULL

> > +		fallthrough;
> > +	default:
> > +		pr_err("Invalid token and IOASID type\n");
> > +		sdata = ERR_PTR(-EINVAL);
> > +		goto exit_unlock;
> >   	}
> >   
> > +	/* REVISIT: may support set w/o quota, use system
> > available */
> > +	if (!quota) {
> > +		sdata = ERR_PTR(-EINVAL);
> > +		goto exit_unlock;
> > +	}
> > +
> > +	sdata = kzalloc(sizeof(*sdata), GFP_ATOMIC);
> > +	if (!sdata) {
> > +		sdata = ERR_PTR(-ENOMEM);
> > +		goto exit_unlock;
> > +	}
> > +
> > +	if (xa_alloc(&ioasid_sets, &id, sdata,
> > +			XA_LIMIT(0, ioasid_capacity_avail - quota),
> > +			GFP_ATOMIC)) {
> > +		kfree(sdata);
> > +		sdata = ERR_PTR(-ENOSPC);
> > +		goto exit_unlock;
> > +	}
> > +
> > +	sdata->token = token;
> > +	sdata->type = type;
> > +	sdata->quota = quota;
> > +	sdata->sid = id;
> > +	refcount_set(&sdata->ref, 1);
> > +
> > +	/*
> > +	 * Per set XA is used to store private IDs within the set,
> > get ready
> > +	 * for ioasid_set private ID and system-wide IOASID
> > allocation
> > +	 * results.
> > +	 */  
> 
> I'm not sure that I understood the per-set XA correctly. Is it used to
> save both private ID and real ID allocated from the system-wide pool?
> If so, isn't private id might be equal to real ID?
> 
> > +	xa_init_flags(&sdata->xa, XA_FLAGS_ALLOC);
> > +	ioasid_capacity_avail -= quota;  
> 
> As mentioned above, the ioasid_set consumed one extra ioasid, so
> 
> 	ioasid_capacity_avail -= (quota + 1);
> 
> ?
> 
Same explanation, make sense?

> > +
> >   exit_unlock:
> >   	spin_unlock(&ioasid_allocator_lock);
> > +
> > +	return sdata;
> >   }
> > -EXPORT_SYMBOL_GPL(ioasid_free);
> > +EXPORT_SYMBOL_GPL(ioasid_alloc_set);
> > +
> > +void ioasid_set_get_locked(struct ioasid_set *set)
> > +{
> > +	if (WARN_ON(xa_load(&ioasid_sets, set->sid) != set)) {
> > +		pr_warn("Invalid set data\n");
> > +		return;
> > +	}
> > +
> > +	refcount_inc(&set->ref);
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_set_get_locked);
> > +
> > +void ioasid_set_get(struct ioasid_set *set)
> > +{
> > +	spin_lock(&ioasid_allocator_lock);
> > +	ioasid_set_get_locked(set);
> > +	spin_unlock(&ioasid_allocator_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_set_get);
> > +
> > +void ioasid_set_put_locked(struct ioasid_set *set)
> > +{
> > +	struct ioasid_data *entry;
> > +	unsigned long index;
> > +
> > +	if (WARN_ON(xa_load(&ioasid_sets, set->sid) != set)) {  
> 
> There are multiple occurences of this line of code, how about defining
> it as a inline helper?
> 
> static inline bool ioasid_is_valid(struct ioasid_set *set)
> {
> 	return xa_load(&ioasid_sets, set->sid) == set;
> }
> 
Sounds good. perhaps the name should be
ioasid_set_is_valid()?

> > +		pr_warn("Invalid set data\n");
> > +		return;
> > +	}
> > +
> > +	if (!refcount_dec_and_test(&set->ref)) {
> > +		pr_debug("%s: IOASID set %d has %d users\n",
> > +			__func__, set->sid,
> > refcount_read(&set->ref));
> > +		return;
> > +	}
> > +
> > +	/* The set is already empty, we just destroy the set. */
> > +	if (xa_empty(&set->xa))
> > +		goto done_destroy;
> > +
> > +	/*
> > +	 * Free all PASIDs from system-wide IOASID pool, all
> > subscribers gets
> > +	 * notified and do cleanup of their own.
> > +	 * Note that some references of the IOASIDs within the set
> > can still
> > +	 * be held after the free call. This is OK in that the
> > IOASIDs will be
> > +	 * marked inactive, the only operations can be done is
> > ioasid_put.
> > +	 * No need to track IOASID set states since there is no
> > reclaim phase.
> > +	 */
> > +	xa_for_each(&set->xa, index, entry) {
> > +		ioasid_free_locked(set, index);
> > +		/* Free from per set private pool */
> > +		xa_erase(&set->xa, index);
> > +	}
> > +
> > +done_destroy:
> > +	/* Return the quota back to system pool */
> > +	ioasid_capacity_avail += set->quota;
> > +	kfree_rcu(set, rcu);
> > +
> > +	/*
> > +	 * Token got released right away after the ioasid_set is
> > freed.
> > +	 * If a new set is created immediately with the newly
> > released token,
> > +	 * it will not allocate the same IOASIDs unless they are
> > reclaimed.
> > +	 */
> > +	xa_erase(&ioasid_sets, set->sid);  
> 
> No. pointer is used after free.
> 
Right, will move it before kfree_rcu.

> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_set_put_locked);
> > +
> > +/**
> > + * ioasid_set_put - Drop a reference to the IOASID set. Free all
> > IOASIDs within
> > + *                  the set if there are no more users.
> > + *
> > + * @set:	The IOASID set ID to be freed
> > + *
> > + * If refcount drops to zero, all IOASIDs allocated within the set
> > will be
> > + * freed.
> > + */
> > +void ioasid_set_put(struct ioasid_set *set)
> > +{
> > +	spin_lock(&ioasid_allocator_lock);
> > +	ioasid_set_put_locked(set);
> > +	spin_unlock(&ioasid_allocator_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_set_put);
> > +
> > +/**
> > + * ioasid_adjust_set - Adjust the quota of an IOASID set
> > + * @set:	IOASID set to be assigned
> > + * @quota:	Quota allowed in this set
> > + *
> > + * Return 0 on success. If the new quota is smaller than the
> > number of
> > + * IOASIDs already allocated, -EINVAL will be returned. No change
> > will be
> > + * made to the existing quota.
> > + */
> > +int ioasid_adjust_set(struct ioasid_set *set, int quota)
> > +{
> > +	int ret = 0;
> > +
> > +	spin_lock(&ioasid_allocator_lock);
> > +	if (set->nr_ioasids > quota) {
> > +		pr_err("New quota %d is smaller than outstanding
> > IOASIDs %d\n",
> > +			quota, set->nr_ioasids);
> > +		ret = -EINVAL;
> > +		goto done_unlock;
> > +	}
> > +
> > +	if (quota >= ioasid_capacity_avail) {  
> 
> This check doesn't make sense since you are updating (not asking for)
> a quota.
> 
> if ((quota > set->quota) &&
>      (quota - set->quota > ioasid_capacity_avail))
> 
Good point, will fix.

Thanks a lot!

> > +		ret = -ENOSPC;
> > +		goto done_unlock;
> > +	}
> > +
> > +	/* Return the delta back to system pool */
> > +	ioasid_capacity_avail += set->quota - quota;  
> 
> ioasid_capacity_avail is defined as a unsigned int, hence this always
> increase the available capacity value even the caller is asking for a
> bigger quota?
> 
> > +
> > +	/*
> > +	 * May have a policy to prevent giving all available
> > IOASIDs
> > +	 * to one set. But we don't enforce here, it should be in
> > the
> > +	 * upper layers.
> > +	 */
> > +	set->quota = quota;
> > +
> > +done_unlock:
> > +	spin_unlock(&ioasid_allocator_lock);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_adjust_set);
> > +
> > +/**
> > + * ioasid_set_for_each_ioasid - Iterate over all the IOASIDs
> > within the set
> > + *
> > + * Caller must hold a reference of the set and handles its own
> > locking.  
> 
> Do you need to hold ioasid_allocator_lock here?
> 
> > + */
> > +int ioasid_set_for_each_ioasid(struct ioasid_set *set,
> > +			       void (*fn)(ioasid_t id, void *data),
> > +			       void *data)
> > +{
> > +	struct ioasid_data *entry;
> > +	unsigned long index;
> > +	int ret = 0;
> > +
> > +	if (xa_empty(&set->xa)) {
> > +		pr_warn("No IOASIDs in the set %d\n", set->sid);
> > +		return -ENOENT;
> > +	}
> > +
> > +	xa_for_each(&set->xa, index, entry) {
> > +		fn(index, data);
> > +	}
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_set_for_each_ioasid);
> >   
> >   /**
> >    * ioasid_find - Find IOASID data
> > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> > index 9c44947a68c8..412d025d440e 100644
> > --- a/include/linux/ioasid.h
> > +++ b/include/linux/ioasid.h
> > @@ -10,8 +10,35 @@ typedef unsigned int ioasid_t;
> >   typedef ioasid_t (*ioasid_alloc_fn_t)(ioasid_t min, ioasid_t max,
> > void *data); typedef void (*ioasid_free_fn_t)(ioasid_t ioasid, void
> > *data); 
> > +/* IOASID set types */
> > +enum ioasid_set_type {
> > +	IOASID_SET_TYPE_NULL = 1, /* Set token is NULL */
> > +	IOASID_SET_TYPE_MM,	  /* Set token is a mm_struct,
> > +				   * i.e. associated with a process
> > +				   */
> > +	IOASID_SET_TYPE_NR,
> > +};
> > +
> > +/**
> > + * struct ioasid_set - Meta data about ioasid_set
> > + * @type:	Token types and other features
> > + * @token:	Unique to identify an IOASID set
> > + * @xa:		XArray to store ioasid_set private IDs, can
> > be used for
> > + *		guest-host IOASID mapping, or just a private
> > IOASID namespace.
> > + * @quota:	Max number of IOASIDs can be allocated within
> > the set
> > + * @nr_ioasids	Number of IOASIDs currently allocated in the
> > set
> > + * @sid:	ID of the set
> > + * @ref:	Reference count of the users
> > + */
> >   struct ioasid_set {
> > -	int dummy;
> > +	void *token;
> > +	struct xarray xa;
> > +	int type;
> > +	int quota;
> > +	int nr_ioasids;
> > +	int sid;
> > +	refcount_t ref;
> > +	struct rcu_head rcu;
> >   };
> >   
> >   /**
> > @@ -29,31 +56,64 @@ struct ioasid_allocator_ops {
> >   	void *pdata;
> >   };
> >   
> > -#define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 }
> > -
> >   #if IS_ENABLED(CONFIG_IOASID)
> > +void ioasid_install_capacity(ioasid_t total);
> > +ioasid_t ioasid_get_capacity(void);
> > +struct ioasid_set *ioasid_alloc_set(void *token, ioasid_t quota,
> > int type); +int ioasid_adjust_set(struct ioasid_set *set, int
> > quota); +void ioasid_set_get_locked(struct ioasid_set *set);
> > +void ioasid_set_put_locked(struct ioasid_set *set);
> > +void ioasid_set_put(struct ioasid_set *set);
> > +
> >   ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
> > ioasid_t max, void *private);
> > -void ioasid_free(ioasid_t ioasid);
> > -void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
> > -		  bool (*getter)(void *));
> > +void ioasid_free(struct ioasid_set *set, ioasid_t ioasid);
> > +
> > +bool ioasid_is_active(ioasid_t ioasid);
> > +
> > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, bool
> > (*getter)(void *)); +int ioasid_attach_data(ioasid_t ioasid, void
> > *data); int ioasid_register_allocator(struct ioasid_allocator_ops
> > *allocator); void ioasid_unregister_allocator(struct
> > ioasid_allocator_ops *allocator); -int ioasid_attach_data(ioasid_t
> > ioasid, void *data); -
> > +void ioasid_is_in_set(struct ioasid_set *set, ioasid_t ioasid);
> > +int ioasid_set_for_each_ioasid(struct ioasid_set *sdata,
> > +			       void (*fn)(ioasid_t id, void *data),
> > +			       void *data);
> >   #else /* !CONFIG_IOASID */
> > +static inline void ioasid_install_capacity(ioasid_t total)
> > +{
> > +}
> > +
> > +static inline ioasid_t ioasid_get_capacity(void)
> > +{
> > +	return 0;
> > +}
> > +
> >   static inline ioasid_t ioasid_alloc(struct ioasid_set *set,
> > ioasid_t min, ioasid_t max, void *private)
> >   {
> >   	return INVALID_IOASID;
> >   }
> >   
> > -static inline void ioasid_free(ioasid_t ioasid)
> > +static inline void ioasid_free(struct ioasid_set *set, ioasid_t
> > ioasid) +{
> > +}
> > +
> > +static inline bool ioasid_is_active(ioasid_t ioasid)
> > +{
> > +	return false;
> > +}
> > +
> > +static inline struct ioasid_set *ioasid_alloc_set(void *token,
> > ioasid_t quota, int type) +{
> > +	return ERR_PTR(-ENOTSUPP);
> > +}
> > +
> > +static inline void ioasid_set_put(struct ioasid_set *set)
> >   {
> >   }
> >   
> > -static inline void *ioasid_find(struct ioasid_set *set, ioasid_t
> > ioasid,
> > -				bool (*getter)(void *))
> > +static inline void *ioasid_find(struct ioasid_set *set, ioasid_t
> > ioasid, bool (*getter)(void *)) {
> >   	return NULL;
> >   }
> >   
> 
> Best regards,
> baolu
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> iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
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[Jacob Pan]