Hi Jason,

On Mon, 10 May 2021 13:39:56 -0300, Jason Gunthorpe <j...@nvidia.com> wrote:

> I still think it is smarter to push a group of RID's into a global
> allocation group and accept there are potential downsides with that
> than to try to force a global allocation group on every RID and then
> try to fix the mess that makes for non-ENQCMD devices.
The proposed ioasid_set change in this set has a token for each set of
IOASIDs.

/**
 * struct ioasid_set - Meta data about ioasid_set
 * @nh:         List of notifiers private to that set
 * @xa:         XArray to store ioasid_set private IDs, can be used for
 *              guest-host IOASID mapping, or just a private IOASID namespace.
 * @token:      Unique to identify an IOASID set
 * @type:       Token types
 * @quota:      Max number of IOASIDs can be allocated within the set
 * @nr_ioasids: Number of IOASIDs currently allocated in the set
 * @id:         ID of the set
 */
struct ioasid_set {
        struct atomic_notifier_head nh;
        struct xarray xa;
        void *token;
        int type;
        int quota;
        atomic_t nr_ioasids;
        int id;
        struct rcu_head rcu;
        struct misc_cg *misc_cg; /* For misc cgroup accounting */
};

To satisfy your "give me a PASID for this RID" proposal, can we just use
the RID's struct device as the token? Also add a type field to explicitly
indicate global vs per-set(per-RID). i.e.

ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
                       int type, void *private)
Where flags can be:
enum ioasid_hwid_type {
        IOASID_HWID_GLOBAL,
        IOASID_HWID_PER_SET,
};

We are really talking about the HW IOASID, just a reminder.

Thanks,

Jacob
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