Re: [PATCH v7 06/10] iommu/sva: Refactoring iommu_sva_bind/unbind_device()

Jean-Philippe Brucker
2022-05-19T16:39:58Z

On Thu, May 19, 2022 at 03:20:43PM +0800, Lu Baolu wrote:
> The existing iommu SVA interfaces are implemented by calling the SVA
> specific iommu ops provided by the IOMMU drivers. There's no need for
> any SVA specific ops in iommu_ops vector anymore as we can achieve
> this through the generic attach/detach_dev_pasid domain ops.
>
> This refactors the IOMMU SVA interfaces implementation by using the
> set/block_pasid_dev ops and align them with the concept of the SVA
> iommu domain. Put the new SVA code in the sva related file in order
> to make it self-contained.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> include/linux/iommu.h | 48 ++++++++------
> drivers/iommu/iommu-sva-lib.h | 1 +
> drivers/iommu/iommu-sva-lib.c | 113 ++++++++++++++++++++++++++++++++
> drivers/iommu/iommu.c | 119 ++++++++--------------------------
> 4 files changed, 170 insertions(+), 111 deletions(-)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index e8cf82d46ce1..d9ac5ebe5bbb 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -635,6 +635,7 @@ struct iommu_fwspec {
> */
> struct iommu_sva {
> struct device *dev;
> + refcount_t users;
> };
>
> int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
> @@ -677,11 +678,6 @@ int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features f);
> int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
> bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
>
> -struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> - struct mm_struct *mm);
> -void iommu_sva_unbind_device(struct iommu_sva *handle);
> -u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> -
> int iommu_device_use_default_domain(struct device *dev);
> void iommu_device_unuse_default_domain(struct device *dev);
>
> @@ -693,6 +689,8 @@ int iommu_set_device_pasid(struct iommu_domain *domain, struct device *dev,
> ioasid_t pasid);
> void iommu_block_device_pasid(struct iommu_domain *domain, struct device *dev,
> ioasid_t pasid);
> +struct iommu_domain *
> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid);
> #else /* CONFIG_IOMMU_API */
>
> struct iommu_ops {};
> @@ -1023,21 +1021,6 @@ iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
> return -ENODEV;
> }
>
> -static inline struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> -{
> - return NULL;
> -}
> -
> -static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
> -{
> -}
> -
> -static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> -{
> - return IOMMU_PASID_INVALID;
> -}
> -
> static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev)
> {
> return NULL;
> @@ -1077,6 +1060,12 @@ static inline void iommu_block_device_pasid(struct iommu_domain *domain,
> struct device *dev, ioasid_t pasid)
> {
> }
> +
> +static inline struct iommu_domain *
> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid)
> +{
> + return NULL;
> +}
> #endif /* CONFIG_IOMMU_API */
>
> /**
> @@ -1108,6 +1097,10 @@ iommu_sva_alloc_domain(struct bus_type *bus, struct mm_struct *mm);
> void iommu_sva_free_domain(struct iommu_domain *domain);
> int iommu_sva_set_domain(struct iommu_domain *domain, struct device *dev,
> ioasid_t pasid);
> +struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> + struct mm_struct *mm);
> +void iommu_sva_unbind_device(struct iommu_sva *handle);
> +u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> #else /* CONFIG_IOMMU_SVA */
> static inline struct iommu_domain *
> iommu_sva_alloc_domain(struct bus_type *bus, struct mm_struct *mm)
> @@ -1124,6 +1117,21 @@ static inline int iommu_sva_set_domain(struct iommu_domain *domain,
> {
> return -EINVAL;
> }
> +
> +static inline struct iommu_sva *
> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> +{
> + return NULL;
> +}
> +
> +static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
> +{
> +}
> +
> +static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> +{
> + return IOMMU_PASID_INVALID;
> +}
> #endif /* CONFIG_IOMMU_SVA */
>
> #endif /* __LINUX_IOMMU_H */
> diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
> index 1be21e6b93ec..ebab5a8cb126 100644
> --- a/drivers/iommu/iommu-sva-lib.h
> +++ b/drivers/iommu/iommu-sva-lib.h
> @@ -20,6 +20,7 @@ struct iopf_queue;
> struct iommu_sva_domain {
> struct iommu_domain domain;
> struct mm_struct *mm;
> + struct iommu_sva bond;
> };
>
> #define to_sva_domain(d) container_of_safe(d, struct iommu_sva_domain, domain)
> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> index 210c376f6043..568e0f64edac 100644
> --- a/drivers/iommu/iommu-sva-lib.c
> +++ b/drivers/iommu/iommu-sva-lib.c
> @@ -4,6 +4,8 @@
> */
> #include <linux/mutex.h>
> #include <linux/sched/mm.h>
> +#include <linux/pci.h>
> +#include <linux/pci-ats.h>
>
> #include "iommu-sva-lib.h"
>
> @@ -117,3 +119,114 @@ int iommu_sva_set_domain(struct iommu_domain *domain, struct device *dev,
>
> return iommu_set_device_pasid(domain, dev, pasid);
> }
> +
> +/**
> + * iommu_sva_bind_device() - Bind a process address space to a device
> + * @dev: the device
> + * @mm: the mm to bind, caller must hold a reference to mm_users
> + *
> + * Create a bond between device and address space, allowing the device to access
> + * the mm using the returned PASID. If a bond already exists between @device and
> + * @mm, it is returned and an additional reference is taken. Caller must call
> + * iommu_sva_unbind_device() to release each reference.
> + *
> + * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
> + * initialize the required SVA features.
> + *
> + * On error, returns an ERR_PTR value.
> + */
> +struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> +{
> + struct iommu_sva_domain *sva_domain;
> + struct iommu_domain *domain;
> + ioasid_t max_pasid = 0;
> + int ret = -EINVAL;
> +
> + /* Allocate mm->pasid if necessary. */
> + if (!dev->iommu->iommu_dev->pasids)
> + return ERR_PTR(-EOPNOTSUPP);
> +
> + if (dev_is_pci(dev)) {
> + max_pasid = pci_max_pasids(to_pci_dev(dev));
> + if (max_pasid < 0)
> + return ERR_PTR(max_pasid);
> + } else {
> + ret = device_property_read_u32(dev, "pasid-num-bits",
> + &max_pasid);
> + if (ret)
> + return ERR_PTR(ret);
> + max_pasid = (1UL << max_pasid);
> + }

The IOMMU driver needs this PASID width information earlier, when creating
the PASID table (in .probe_device(), .attach_dev()). Since we're moving it
to the IOMMU core to avoid code duplication, it should be done earlier and
stored in dev->iommu

Thanks,
Jean

> + max_pasid = min_t(u32, max_pasid, dev->iommu->iommu_dev->pasids);
> + ret = iommu_sva_alloc_pasid(mm, 1, max_pasid - 1);
> + if (ret)
> + return ERR_PTR(ret);
> +
> + mutex_lock(&iommu_sva_lock);
> + /* Search for an existing domain. */
> + domain = iommu_get_domain_for_dev_pasid(dev, mm->pasid);
> + if (domain) {
> + sva_domain = to_sva_domain(domain);
> + refcount_inc(&sva_domain->bond.users);
> + goto out_success;
> + }
> +
> + /* Allocate a new domain and set it on device pasid. */
> + domain = iommu_sva_alloc_domain(dev->bus, mm);
> + if (IS_ERR(domain)) {
> + ret = PTR_ERR(domain);
> + goto out_unlock;
> + }
> +
> + ret = iommu_sva_set_domain(domain, dev, mm->pasid);
> + if (ret)
> + goto out_free_domain;
> + sva_domain = to_sva_domain(domain);
> + sva_domain->bond.dev = dev;
> + refcount_set(&sva_domain->bond.users, 1);
> +
> +out_success:
> + mutex_unlock(&iommu_sva_lock);
> + return &sva_domain->bond;
> +
> +out_free_domain:
> + iommu_sva_free_domain(domain);
> +out_unlock:
> + mutex_unlock(&iommu_sva_lock);
> +
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
> +
> +/**
> + * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
> + * @handle: the handle returned by iommu_sva_bind_device()
> + *
> + * Put reference to a bond between device and address space. The device should
> + * not be issuing any more transaction for this PASID. All outstanding page
> + * requests for this PASID must have been flushed to the IOMMU.
> + */
> +void iommu_sva_unbind_device(struct iommu_sva *handle)
> +{
> + struct device *dev = handle->dev;
> + struct iommu_sva_domain *sva_domain =
> + container_of(handle, struct iommu_sva_domain, bond);
> + ioasid_t pasid = iommu_sva_get_pasid(handle);
> +
> + mutex_lock(&iommu_sva_lock);
> + if (refcount_dec_and_test(&sva_domain->bond.users)) {
> + iommu_block_device_pasid(&sva_domain->domain, dev, pasid);
> + iommu_sva_free_domain(&sva_domain->domain);
> + }
> + mutex_unlock(&iommu_sva_lock);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
> +
> +u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> +{
> + struct iommu_sva_domain *sva_domain =
> + container_of(handle, struct iommu_sva_domain, bond);
> +
> + return sva_domain->mm->pasid;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 789816e4b9d6..e49c5a5b8cc1 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2766,97 +2766,6 @@ bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)
> }
> EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
>
> -/**
> - * iommu_sva_bind_device() - Bind a process address space to a device
> - * @dev: the device
> - * @mm: the mm to bind, caller must hold a reference to it
> - *
> - * Create a bond between device and address space, allowing the device to access
> - * the mm using the returned PASID. If a bond already exists between @device and
> - * @mm, it is returned and an additional reference is taken. Caller must call
> - * iommu_sva_unbind_device() to release each reference.
> - *
> - * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
> - * initialize the required SVA features.
> - *
> - * On error, returns an ERR_PTR value.
> - */
> -struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> -{
> - struct iommu_group *group;
> - struct iommu_sva *handle = ERR_PTR(-EINVAL);
> - const struct iommu_ops *ops = dev_iommu_ops(dev);
> -
> - if (!ops->sva_bind)
> - return ERR_PTR(-ENODEV);
> -
> - group = iommu_group_get(dev);
> - if (!group)
> - return ERR_PTR(-ENODEV);
> -
> - /* Ensure device count and domain don't change while we're binding */
> - mutex_lock(&group->mutex);
> -
> - /*
> - * To keep things simple, SVA currently doesn't support IOMMU groups
> - * with more than one device. Existing SVA-capable systems are not
> - * affected by the problems that required IOMMU groups (lack of ACS
> - * isolation, device ID aliasing and other hardware issues).
> - */
> - if (iommu_group_device_count(group) != 1)
> - goto out_unlock;
> -
> - handle = ops->sva_bind(dev, mm);
> -
> -out_unlock:
> - mutex_unlock(&group->mutex);
> - iommu_group_put(group);
> -
> - return handle;
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
> -
> -/**
> - * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
> - * @handle: the handle returned by iommu_sva_bind_device()
> - *
> - * Put reference to a bond between device and address space. The device should
> - * not be issuing any more transaction for this PASID. All outstanding page
> - * requests for this PASID must have been flushed to the IOMMU.
> - */
> -void iommu_sva_unbind_device(struct iommu_sva *handle)
> -{
> - struct iommu_group *group;
> - struct device *dev = handle->dev;
> - const struct iommu_ops *ops = dev_iommu_ops(dev);
> -
> - if (!ops->sva_unbind)
> - return;
> -
> - group = iommu_group_get(dev);
> - if (!group)
> - return;
> -
> - mutex_lock(&group->mutex);
> - ops->sva_unbind(handle);
> - mutex_unlock(&group->mutex);
> -
> - iommu_group_put(group);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
> -
> -u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> -{
> - const struct iommu_ops *ops = dev_iommu_ops(handle->dev);
> -
> - if (!ops->sva_get_pasid)
> - return IOMMU_PASID_INVALID;
> -
> - return ops->sva_get_pasid(handle);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
> -
> /*
> * Changes the default domain of an iommu group that has *only* one device
> *
> @@ -3322,3 +3231,31 @@ void iommu_block_device_pasid(struct iommu_domain *domain, struct device *dev,
>
> iommu_group_put(group);
> }
> +
> +/*
> + * This is a variant of iommu_get_domain_for_dev(). It returns the existing
> + * domain attached to pasid of a device. It's only for internal use of the
> + * IOMMU subsystem. The caller must take care to avoid any possible
> + * use-after-free case.
> + */
> +struct iommu_domain *
> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid)
> +{
> + struct iommu_domain *domain;
> + struct iommu_group *group;
> +
> + if (!pasid_valid(pasid))
> + return NULL;
> +
> + group = iommu_group_get(dev);
> + if (!group)
> + return NULL;
> + /*
> + * The xarray protects its internal state with RCU. Hence the domain
> + * obtained is either NULL or fully formed.
> + */
> + domain = xa_load(&group->pasid_array, pasid);
> + iommu_group_put(group);
> +
> + return domain;
> +}
> --
> 2.25.1
>