Re: [PATCH v3 09/14] iommu/ioasid: Introduce ioasid_set private ID

Jean-Philippe Brucker
2020-10-23T11:40:07Z

On Mon, Sep 28, 2020 at 02:38:36PM -0700, Jacob Pan wrote:
> When an IOASID set is used for guest SVA, each VM will acquire its
> ioasid_set for IOASID allocations. IOASIDs within the VM must have a
> host/physical IOASID backing, mapping between guest and host IOASIDs can
> be non-identical. IOASID set private ID (SPID) is introduced in this
> patch to be used as guest IOASID. However, the concept of ioasid_set
> specific namespace is generic, thus named SPID.
>
> As SPID namespace is within the IOASID set, the IOASID core can provide
> lookup services at both directions. SPIDs may not be available when its
> IOASID is allocated, the mapping between SPID and IOASID is usually
> established when a guest page table is bound to a host PASID.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> drivers/iommu/ioasid.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/ioasid.h | 19 +++++++++
> 2 files changed, 121 insertions(+)
>
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index 828cc44b1b1c..378fef8f23d9 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -26,6 +26,7 @@ enum ioasid_state {
> * struct ioasid_data - Meta data about ioasid
> *
> * @id: Unique ID
> + * @spid: Private ID unique within a set
> * @users: Number of active users
> * @state: Track state of the IOASID
> * @set: ioasid_set of the IOASID belongs to
> @@ -34,6 +35,7 @@ enum ioasid_state {
> */
> struct ioasid_data {
> ioasid_t id;
> + ioasid_t spid;
> refcount_t users;
> enum ioasid_state state;
> struct ioasid_set *set;
> @@ -363,6 +365,105 @@ void ioasid_detach_data(ioasid_t ioasid)
> }
> EXPORT_SYMBOL_GPL(ioasid_detach_data);
>
> +static ioasid_t ioasid_find_by_spid_locked(struct ioasid_set *set, ioasid_t spid)
> +{
> + ioasid_t ioasid = INVALID_IOASID;
> + struct ioasid_data *entry;
> + unsigned long index;
> +
> + if (!xa_load(&ioasid_sets, set->id)) {
> + pr_warn("Invalid set\n");

Could use ioasid_set_is_valid(), and perhaps a WARN_ON() instead of
pr_warn() since this is a programming error.

> + goto done;

Or just return INVALID_IOASID

> + }
> +
> + xa_for_each(&set->xa, index, entry) {
> + if (spid == entry->spid) {
> + refcount_inc(&entry->users);
> + ioasid = index;

break

> + }
> + }
> +done:
> + return ioasid;
> +}
> +
> +/**
> + * ioasid_attach_spid - Attach ioasid_set private ID to an IOASID
> + *
> + * @ioasid: the system-wide IOASID to attach
> + * @spid: the ioasid_set private ID of @ioasid
> + *
> + * After attching SPID, future lookup can be done via ioasid_find_by_spid().

attaching

> + */
> +int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
> +{
> + struct ioasid_data *data;
> + int ret = 0;
> +
> + if (spid == INVALID_IOASID)
> + return -EINVAL;
> +
> + spin_lock(&ioasid_allocator_lock);
> + data = xa_load(&active_allocator->xa, ioasid);
> +
> + if (!data) {
> + pr_err("No IOASID entry %d to attach SPID %d\n",
> + ioasid, spid);
> + ret = -ENOENT;
> + goto done_unlock;
> + }
> + /* Check if SPID is unique within the set */
> + if (ioasid_find_by_spid_locked(data->set, spid) != INVALID_IOASID) {

We need an additional parameter to ioasid_find_by_spid_locked(), telling
it not to take a reference to the conflicting entry. Here we return with
the reference, which will never be released.

> + ret = -EINVAL;
> + goto done_unlock;
> + }
> + data->spid = spid;
> +
> +done_unlock:
> + spin_unlock(&ioasid_allocator_lock);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(ioasid_attach_spid);
> +
> +void ioasid_detach_spid(ioasid_t ioasid)

Could add a small comment to this public function

Thanks,
Jean

> +{
> + struct ioasid_data *data;
> +
> + spin_lock(&ioasid_allocator_lock);
> + data = xa_load(&active_allocator->xa, ioasid);
> +
> + if (!data || data->spid == INVALID_IOASID) {
> + pr_err("Invalid IOASID entry %d to detach\n", ioasid);
> + goto done_unlock;
> + }
> + data->spid = INVALID_IOASID;
> +
> +done_unlock:
> + spin_unlock(&ioasid_allocator_lock);
> +}
> +EXPORT_SYMBOL_GPL(ioasid_detach_spid);
> +
> +/**
> + * ioasid_find_by_spid - Find the system-wide IOASID by a set private ID and
> + * its set.
> + *
> + * @set: the ioasid_set to search within
> + * @spid: the set private ID
> + *
> + * Given a set private ID and its IOASID set, find the system-wide IOASID. Take
> + * a reference upon finding the matching IOASID. Return INVALID_IOASID if the
> + * IOASID is not found in the set or the set is not valid.
> + */
> +ioasid_t ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid)
> +{
> + ioasid_t ioasid;
> +
> + spin_lock(&ioasid_allocator_lock);
> + ioasid = ioasid_find_by_spid_locked(set, spid);
> + spin_unlock(&ioasid_allocator_lock);
> + return ioasid;
> +}
> +EXPORT_SYMBOL_GPL(ioasid_find_by_spid);
> +
> static inline bool ioasid_set_is_valid(struct ioasid_set *set)
> {
> return xa_load(&ioasid_sets, set->id) == set;
> @@ -529,6 +630,7 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
> goto exit_free;
> }
> data->id = id;
> + data->spid = INVALID_IOASID;
> data->state = IOASID_STATE_ACTIVE;
> refcount_set(&data->users, 1);
>
> diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> index 16d421357173..2dfe85e6cb7e 100644
> --- a/include/linux/ioasid.h
> +++ b/include/linux/ioasid.h
> @@ -79,6 +79,10 @@ bool ioasid_put(struct ioasid_set *set, ioasid_t ioasid);
> bool ioasid_put_locked(struct ioasid_set *set, ioasid_t ioasid);
> int ioasid_attach_data(ioasid_t ioasid, void *data);
> void ioasid_detach_data(ioasid_t ioasid);
> +int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid);
> +void ioasid_detach_spid(ioasid_t ioasid);
> +ioasid_t ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid);
> +
> void ioasid_set_for_each_ioasid(struct ioasid_set *sdata,
> void (*fn)(ioasid_t id, void *data),
> void *data);
> @@ -159,6 +163,21 @@ static inline void ioasid_detach_data(ioasid_t ioasid)
> {
> }
>
> +static inline int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
> +{
> + return -ENOTSUPP;
> +}
> +
> +static inline void ioasid_detach_spid(ioasid_t ioasid)
> +{
> +}
> +
> +static inline ioasid_t ioasid_find_by_spid(struct ioasid_set *set,
> + ioasid_t spid)
> +{
> + return INVALID_IOASID;
> +}
> +
> static inline void ioasid_set_for_each_ioasid(struct ioasid_set *sdata,
> void (*fn)(ioasid_t id, void *data),
> void *data)
> --
> 2.7.4
>