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iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit 

PASIDs are process-wide. It was attempted to use refcounted PASIDs to
free them when the last thread drops the refcount. This turned out to
be complex and error prone. Given the fact that the PASID space is 20
bits, which allows up to 1M processes to have a PASID associated
concurrently, PASID resource exhaustion is not a realistic concern.

Therefore, it was decided to simplify the approach and stick with lazy
on demand PASID allocation, but drop the eager free approach and make an
allocated PASID's lifetime bound to the lifetime of the process.

Get rid of the refcounting mechanisms and replace/rename the interfaces
to reflect this new approach.

  [ bp: Massage commit message. ]

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20220207230254.3342514-6-fenghua.yu@intel.com
This commit is contained in:
Fenghua Yu 2022-02-07 15:02:48 -08:00 committed by Borislav Petkov
parent a6cbd44093
commit 701fac4038
9 changed files with 38 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
View File

@ -340,14 +340,12 @@ __arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm)
bond->smmu_mn = arm_smmu_mmu_notifier_get(smmu_domain, mm);
if (IS_ERR(bond->smmu_mn)) {
ret = PTR_ERR(bond->smmu_mn);
goto err_free_pasid;
goto err_free_bond;
}
list_add(&bond->list, &master->bonds);
return &bond->sva;
err_free_pasid:
iommu_sva_free_pasid(mm);
err_free_bond:
kfree(bond);
return ERR_PTR(ret);
@ -377,7 +375,6 @@ void arm_smmu_sva_unbind(struct iommu_sva *handle)
if (refcount_dec_and_test(&bond->refs)) {
list_del(&bond->list);
arm_smmu_mmu_notifier_put(bond->smmu_mn);
iommu_sva_free_pasid(bond->mm);
kfree(bond);
}
mutex_unlock(&sva_lock);

4
drivers/iommu/intel/iommu.c
View File

@ -4781,7 +4781,7 @@ attach_failed:
link_failed:
spin_unlock_irqrestore(&device_domain_lock, flags);
if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
ioasid_put(domain->default_pasid);
ioasid_free(domain->default_pasid);
return ret;
}
@ -4811,7 +4811,7 @@ static void aux_domain_remove_dev(struct dmar_domain *domain,
spin_unlock_irqrestore(&device_domain_lock, flags);
if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
ioasid_put(domain->default_pasid);
ioasid_free(domain->default_pasid);
}
static int prepare_domain_attach_device(struct iommu_domain *domain,

9
drivers/iommu/intel/svm.c
View File

@ -514,11 +514,6 @@ static int intel_svm_alloc_pasid(struct device *dev, struct mm_struct *mm,
return iommu_sva_alloc_pasid(mm, PASID_MIN, max_pasid - 1);
}
static void intel_svm_free_pasid(struct mm_struct *mm)
{
iommu_sva_free_pasid(mm);
}
static struct iommu_sva *intel_svm_bind_mm(struct intel_iommu *iommu,
struct device *dev,
struct mm_struct *mm,
@ -662,8 +657,6 @@ static int intel_svm_unbind_mm(struct device *dev, u32 pasid)
kfree(svm);
}
}
/* Drop a PASID reference and free it if no reference. */
intel_svm_free_pasid(mm);
}
out:
return ret;
@ -1047,8 +1040,6 @@ struct iommu_sva *intel_svm_bind(struct device *dev, struct mm_struct *mm, void
}
sva = intel_svm_bind_mm(iommu, dev, mm, flags);
if (IS_ERR_OR_NULL(sva))
intel_svm_free_pasid(mm);
mutex_unlock(&pasid_mutex);
return sva;

39
drivers/iommu/ioasid.c
View File

@ -2,7 +2,7 @@
/*
* 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_put.
* free IOASIDs with ioasid_alloc() and ioasid_free().
*/
#include <linux/ioasid.h>
#include <linux/module.h>
@ -15,7 +15,6 @@ struct ioasid_data {
struct ioasid_set *set;
void *private;
struct rcu_head rcu;
refcount_t refs;
};
/*
@ -315,7 +314,6 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
data->set = set;
data->private = private;
refcount_set(&data->refs, 1);
/*
* Custom allocator needs allocator data to perform platform specific
@ -348,35 +346,11 @@ exit_free:
EXPORT_SYMBOL_GPL(ioasid_alloc);
/**
* ioasid_get - obtain a reference to the IOASID
* @ioasid: the ID to get
*/
void ioasid_get(ioasid_t ioasid)
{
struct ioasid_data *ioasid_data;
spin_lock(&ioasid_allocator_lock);
ioasid_data = xa_load(&active_allocator->xa, ioasid);
if (ioasid_data)
refcount_inc(&ioasid_data->refs);
else
WARN_ON(1);
spin_unlock(&ioasid_allocator_lock);
}
EXPORT_SYMBOL_GPL(ioasid_get);
/**
* ioasid_put - Release a reference to an ioasid
* ioasid_free - Free an ioasid
* @ioasid: the ID to remove
*
* Put a reference to the IOASID, free it when the number of references drops to
* zero.
*
* Return: %true if the IOASID was freed, %false otherwise.
*/
bool ioasid_put(ioasid_t ioasid)
void ioasid_free(ioasid_t ioasid)
{
bool free = false;
struct ioasid_data *ioasid_data;
spin_lock(&ioasid_allocator_lock);
@ -386,10 +360,6 @@ bool ioasid_put(ioasid_t ioasid)
goto exit_unlock;
}
free = refcount_dec_and_test(&ioasid_data->refs);
if (!free)
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) {
@ -399,9 +369,8 @@ bool ioasid_put(ioasid_t ioasid)
exit_unlock:
spin_unlock(&ioasid_allocator_lock);
return free;
}
EXPORT_SYMBOL_GPL(ioasid_put);
EXPORT_SYMBOL_GPL(ioasid_free);
/**
* ioasid_find - Find IOASID data

39
drivers/iommu/iommu-sva-lib.c
View File

@ -18,8 +18,7 @@ static DECLARE_IOASID_SET(iommu_sva_pasid);
*
* Try to allocate a PASID for this mm, or take a reference to the existing one
* provided it fits within the [@min, @max] range. On success the PASID is
* available in mm->pasid, and must be released with iommu_sva_free_pasid().
* @min must be greater than 0, because 0 indicates an unused mm->pasid.
* available in mm->pasid and will be available for the lifetime of the mm.
*
* Returns 0 on success and < 0 on error.
*/
@ -33,38 +32,24 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
return -EINVAL;
mutex_lock(&iommu_sva_lock);
if (mm->pasid) {
if (mm->pasid >= min && mm->pasid <= max)
ioasid_get(mm->pasid);
else
/* Is a PASID already associated with this mm? */
if (pasid_valid(mm->pasid)) {
if (mm->pasid < min || mm->pasid >= max)
ret = -EOVERFLOW;
} else {
pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
if (pasid == INVALID_IOASID)
ret = -ENOMEM;
else
mm->pasid = pasid;
goto out;
}
pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
if (!pasid_valid(pasid))
ret = -ENOMEM;
else
mm_pasid_set(mm, pasid);
out:
mutex_unlock(&iommu_sva_lock);
return ret;
}
EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
/**
* iommu_sva_free_pasid - Release the mm's PASID
* @mm: the mm
*
* Drop one reference to a PASID allocated with iommu_sva_alloc_pasid()
*/
void iommu_sva_free_pasid(struct mm_struct *mm)
{
mutex_lock(&iommu_sva_lock);
if (ioasid_put(mm->pasid))
mm->pasid = 0;
mutex_unlock(&iommu_sva_lock);
}
EXPORT_SYMBOL_GPL(iommu_sva_free_pasid);
/* ioasid_find getter() requires a void * argument */
static bool __mmget_not_zero(void *mm)
{

1
drivers/iommu/iommu-sva-lib.h
View File

@ -9,7 +9,6 @@
#include <linux/mm_types.h>
int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
void iommu_sva_free_pasid(struct mm_struct *mm);
struct mm_struct *iommu_sva_find(ioasid_t pasid);
/* I/O Page fault */

12
include/linux/ioasid.h
View File

@ -34,8 +34,7 @@ struct ioasid_allocator_ops {
#if IS_ENABLED(CONFIG_IOASID)
ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
void *private);
void ioasid_get(ioasid_t ioasid);
bool ioasid_put(ioasid_t ioasid);
void ioasid_free(ioasid_t ioasid);
void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
bool (*getter)(void *));
int ioasid_register_allocator(struct ioasid_allocator_ops *allocator);
@ -53,14 +52,7 @@ static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
return INVALID_IOASID;
}
static inline void ioasid_get(ioasid_t ioasid)
{
}
static inline bool ioasid_put(ioasid_t ioasid)
{
return false;
}
static inline void ioasid_free(ioasid_t ioasid) { }
static inline void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
bool (*getter)(void *))

16
include/linux/sched/mm.h
View File

@ -439,8 +439,24 @@ static inline void mm_pasid_init(struct mm_struct *mm)
{
mm->pasid = INVALID_IOASID;
}
/* Associate a PASID with an mm_struct: */
static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid)
{
mm->pasid = pasid;
}
static inline void mm_pasid_drop(struct mm_struct *mm)
{
if (pasid_valid(mm->pasid)) {
ioasid_free(mm->pasid);
mm->pasid = INVALID_IOASID;
}
}
#else
static inline void mm_pasid_init(struct mm_struct *mm) {}
static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid) {}
static inline void mm_pasid_drop(struct mm_struct *mm) {}
#endif
#endif /* _LINUX_SCHED_MM_H */

1
kernel/fork.c
View File

@ -1115,6 +1115,7 @@ static inline void __mmput(struct mm_struct *mm)
}
if (mm->binfmt)
module_put(mm->binfmt->module);
mm_pasid_drop(mm);
mmdrop(mm);
}