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Date: Fri, 27 Mar 2020 09:55:43 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Jacob Pan <jacob.jun.pan@...ux.intel.com>,
Joerg Roedel <joro@...tes.org>,
Alex Williamson <alex.williamson@...hat.com>,
Lu Baolu <baolu.lu@...ux.intel.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
David Woodhouse <dwmw2@...radead.org>,
Jean-Philippe Brucker <jean-philippe@...aro.com>
CC: "Liu, Yi L" <yi.l.liu@...el.com>,
"Raj, Ashok" <ashok.raj@...el.com>,
Christoph Hellwig <hch@...radead.org>,
Jonathan Cameron <jic23@...nel.org>,
Eric Auger <eric.auger@...hat.com>
Subject: RE: [PATCH 07/10] iommu/ioasid: Use mutex instead of spinlock
> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Sent: Thursday, March 26, 2020 1:55 AM
>
> Each IOASID or set could have multiple users with its own HW context
> to maintain. Often times access to the HW context requires thread context.
> For example, consumers of IOASIDs can register notification blocks to
> sync up its states. Having an atomic notifier is not feasible for these
> update operations.
>
> This patch converts allocator lock from spinlock to mutex in preparation
> for IOASID notifier.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
> drivers/iommu/ioasid.c | 45 +++++++++++++++++++++++----------------------
> 1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index f89a595f6978..8612fe6477dc 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -98,7 +98,7 @@ struct ioasid_allocator_data {
> struct rcu_head rcu;
> };
>
> -static DEFINE_SPINLOCK(ioasid_allocator_lock);
> +static DEFINE_MUTEX(ioasid_allocator_lock);
> static LIST_HEAD(allocators_list);
>
> static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
> @@ -121,7 +121,7 @@ static ioasid_t default_alloc(ioasid_t min, ioasid_t
> max, void *opaque)
> {
> ioasid_t id;
>
> - if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max),
> GFP_ATOMIC)) {
> + if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max),
> GFP_KERNEL)) {
> pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
> return INVALID_IOASID;
> }
> @@ -142,7 +142,7 @@ static struct ioasid_allocator_data
> *ioasid_alloc_allocator(struct ioasid_alloca
> {
> struct ioasid_allocator_data *ia_data;
>
> - ia_data = kzalloc(sizeof(*ia_data), GFP_ATOMIC);
> + ia_data = kzalloc(sizeof(*ia_data), GFP_KERNEL);
> if (!ia_data)
> return NULL;
>
> @@ -184,7 +184,7 @@ int ioasid_register_allocator(struct
> ioasid_allocator_ops *ops)
> struct ioasid_allocator_data *pallocator;
> int ret = 0;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
>
> ia_data = ioasid_alloc_allocator(ops);
> if (!ia_data) {
> @@ -228,12 +228,12 @@ int ioasid_register_allocator(struct
> ioasid_allocator_ops *ops)
> }
> list_add_tail(&ia_data->list, &allocators_list);
>
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> return 0;
> out_free:
> kfree(ia_data);
> out_unlock:
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> return ret;
> }
> EXPORT_SYMBOL_GPL(ioasid_register_allocator);
> @@ -251,7 +251,7 @@ void ioasid_unregister_allocator(struct
> ioasid_allocator_ops *ops)
> struct ioasid_allocator_data *pallocator;
> struct ioasid_allocator_ops *sops;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
> if (list_empty(&allocators_list)) {
> pr_warn("No custom IOASID allocators active!\n");
> goto exit_unlock;
> @@ -296,7 +296,7 @@ void ioasid_unregister_allocator(struct
> ioasid_allocator_ops *ops)
> }
>
> exit_unlock:
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> }
> EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);
>
> @@ -313,13 +313,13 @@ int ioasid_attach_data(ioasid_t ioasid, void *data)
> struct ioasid_data *ioasid_data;
> int ret = 0;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
> ioasid_data = xa_load(&active_allocator->xa, ioasid);
> if (ioasid_data)
> rcu_assign_pointer(ioasid_data->private, data);
> else
> ret = -ENOENT;
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
>
> /*
> * Wait for readers to stop accessing the old private data, so the
> @@ -374,7 +374,7 @@ ioasid_t ioasid_alloc(int sid, ioasid_t min, ioasid_t
> max, void *private)
> * Custom allocator needs allocator data to perform platform specific
> * operations.
> */
> - spin_lock(&ioasid_allocator_lock);
> + mutex_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) {
> @@ -383,7 +383,7 @@ ioasid_t ioasid_alloc(int sid, ioasid_t min, ioasid_t
> max, void *private)
> }
>
> if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
> - xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id),
> GFP_ATOMIC)) {
> + xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id),
> GFP_KERNEL)) {
> /* Custom allocator needs framework to store and track
> allocation results */
> pr_err("Failed to alloc ioasid from %d\n", id);
> active_allocator->ops->free(id, active_allocator->ops->pdata);
> @@ -394,10 +394,11 @@ ioasid_t ioasid_alloc(int sid, ioasid_t min, ioasid_t
> max, void *private)
> /* Store IOASID in the per set data */
> xa_store(&sdata->xa, id, data, GFP_KERNEL);
> sdata->nr_ioasids++;
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> +
> return id;
> exit_free:
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> kfree(data);
> return INVALID_IOASID;
> }
> @@ -440,9 +441,9 @@ static void ioasid_free_locked(ioasid_t ioasid)
> */
> void ioasid_free(ioasid_t ioasid)
> {
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
> ioasid_free_locked(ioasid);
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> }
> EXPORT_SYMBOL_GPL(ioasid_free);
>
> @@ -473,7 +474,7 @@ int ioasid_alloc_set(struct ioasid_set *token, ioasid_t
> quota, int *sid)
> if (!sdata)
> return -ENOMEM;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
>
> ret = xa_alloc(&ioasid_sets, &id, sdata,
> XA_LIMIT(0, ioasid_capacity_avail - quota),
> @@ -497,7 +498,7 @@ int ioasid_alloc_set(struct ioasid_set *token, ioasid_t
> quota, int *sid)
> *sid = id;
>
> error:
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
>
> return ret;
> }
> @@ -518,7 +519,7 @@ void ioasid_free_set(int sid, bool destroy_set)
> struct ioasid_data *entry;
> unsigned long index;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
> sdata = xa_load(&ioasid_sets, sid);
> if (!sdata) {
> pr_err("No IOASID set found to free %d\n", sid);
> @@ -549,7 +550,7 @@ void ioasid_free_set(int sid, bool destroy_set)
> }
>
> done_unlock:
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
> }
> EXPORT_SYMBOL_GPL(ioasid_free_set);
>
> @@ -613,11 +614,11 @@ int ioasid_find_sid(ioasid_t ioasid)
> struct ioasid_data *ioasid_data;
> int ret = 0;
>
> - spin_lock(&ioasid_allocator_lock);
> + mutex_lock(&ioasid_allocator_lock);
> ioasid_data = xa_load(&active_allocator->xa, ioasid);
> ret = (ioasid_data) ? ioasid_data->sdata->sid : -ENOENT;
>
> - spin_unlock(&ioasid_allocator_lock);
> + mutex_unlock(&ioasid_allocator_lock);
>
> return ret;
> }
> --
> 2.7.4
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
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