Hi Sumit,
Thank you so much for the comemnts :).
On 11/23/2024 9:32 PM, Sumit Garg wrote:
> Hi Amirreza,
>
> Thanks for proposing this.
>
> On Fri, 22 Nov 2024 at 06:38, Amirreza Zarrabi
> <quic_azarrabi@xxxxxxxxxxx> wrote:
>>
>>
>> On 11/21/2024 11:08 PM, Jens Wiklander wrote:
>>
>> Hi Jens,
>>
>>> Hi Amirreza,
>>>
>>> On Thu, Nov 21, 2024 at 2:37 AM Amirreza Zarrabi
>>> <quic_azarrabi@xxxxxxxxxxx> wrote:
>>>>
>>>> The default context has a lifespan similar to the tee_device.
>
> Since it's associated with tee_device context, let's call it obvious
> via renaming it as device context instead (s/def_ctx/dev_ctx/ in this
> patch).
>
Make sense, I'll rename it.
>>>> It is used as a context for shared memory if the context to which the
>>>> shared memory belongs is released, making the tee_shm an orphan.
>>>> This allows the driver implementing shm_unregister to safely make
>>>> subsequent calls, such as to a supplicant if needed.
>>>>
>>>> It also enables users to free the shared memory while the driver is
>>>> blocked on unregister_tee_device safely.
>>>>
>>>> Preferably, this should be used for all driver internal uses, using
>>>> teedev_get_def_context rather than calling teedev_open.
>
> Makes sense to me.
>
>>>>
>>>> Signed-off-by: Amirreza Zarrabi <quic_azarrabi@xxxxxxxxxxx>
>>>> ---
>>>> drivers/tee/optee/core.c | 2 +-
>>>> drivers/tee/optee/ffa_abi.c | 2 +-
>>>> drivers/tee/optee/smc_abi.c | 2 +-
>>>> drivers/tee/tee_core.c | 83 +++++++++++++++++++++++++++++----------------
>>>> drivers/tee/tee_private.h | 3 --
>>>> drivers/tee/tee_shm.c | 18 ++--------
>>>> include/linux/tee_core.h | 15 ++++++++
>>>> include/linux/tee_drv.h | 7 ----
>>>> 8 files changed, 73 insertions(+), 59 deletions(-)
>>>>
>>>> diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
>>>> index c75fddc83576..78d43d0c8014 100644
>>>> --- a/drivers/tee/optee/core.c
>>>> +++ b/drivers/tee/optee/core.c
>>>> @@ -173,7 +173,7 @@ void optee_remove_common(struct optee *optee)
>>>>
>>>> optee_notif_uninit(optee);
>>>> optee_shm_arg_cache_uninit(optee);
>>>> - teedev_close_context(optee->ctx);
>>>> +
>>>> /*
>>>> * The two devices have to be unregistered before we can free the
>>>> * other resources.
>>>> diff --git a/drivers/tee/optee/ffa_abi.c b/drivers/tee/optee/ffa_abi.c
>>>> index f3af5666bb11..6ad94f0788ad 100644
>>>> --- a/drivers/tee/optee/ffa_abi.c
>>>> +++ b/drivers/tee/optee/ffa_abi.c
>>>> @@ -949,7 +949,7 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev)
>>>> optee_shm_arg_cache_init(optee, arg_cache_flags);
>>>> mutex_init(&optee->rpmb_dev_mutex);
>>>> ffa_dev_set_drvdata(ffa_dev, optee);
>>>> - ctx = teedev_open(optee->teedev);
>>>> + ctx = teedev_get_def_context(optee->teedev);
>>>> if (IS_ERR(ctx)) {
>>>> rc = PTR_ERR(ctx);
>>>> goto err_rhashtable_free;
>>>> diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
>>>> index e9456e3e74cc..c77a3e631d04 100644
>>>> --- a/drivers/tee/optee/smc_abi.c
>>>> +++ b/drivers/tee/optee/smc_abi.c
>>>> @@ -1722,7 +1722,7 @@ static int optee_probe(struct platform_device *pdev)
>>>> mutex_init(&optee->rpmb_dev_mutex);
>>>>
>>>> platform_set_drvdata(pdev, optee);
>>>> - ctx = teedev_open(optee->teedev);
>>>> + ctx = teedev_get_def_context(optee->teedev);
>>>> if (IS_ERR(ctx)) {
>>>> rc = PTR_ERR(ctx);
>>>> goto err_supp_uninit;
>>>> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
>>>> index 93f3b330aec8..805e1336089d 100644
>>>> --- a/drivers/tee/tee_core.c
>>>> +++ b/drivers/tee/tee_core.c
>>>> @@ -57,7 +57,6 @@ struct tee_context *teedev_open(struct tee_device *teedev)
>>>> goto err;
>>>> }
>>>>
>>>> - kref_init(&ctx->refcount);
>>>> ctx->teedev = teedev;
>>>> INIT_LIST_HEAD(&ctx->list_shm);
>>>> rc = teedev->desc->ops->open(ctx);
>>>> @@ -73,36 +72,43 @@ struct tee_context *teedev_open(struct tee_device *teedev)
>>>> }
>>>> EXPORT_SYMBOL_GPL(teedev_open);
>>>>
>>>> -void teedev_ctx_get(struct tee_context *ctx)
>>>> +struct tee_context *teedev_get_def_context(struct tee_device *teedev)
>>>> {
>>>> - if (ctx->releasing)
>>>> - return;
>>>> + int rc;
>>>> + struct tee_context *ctx = &teedev->def_ctx;
>>>>
>>>> - kref_get(&ctx->refcount);
>>>> -}
>>>> + ctx->teedev = teedev;
>>>> + INIT_LIST_HEAD(&ctx->list_shm);
>>>> + rc = teedev->desc->ops->open(ctx);
>>>> + if (rc)
>>>> + return ERR_PTR(rc);
>>>
>>> I think ctx->teedev and ctx->list_shm must always be initialized or
>>> &teedev->def_ctx can't be used in teedev_close_context().
>>
>> True, but &teedev->def_ctx is never used in teedev_close_context().
>> The closing of the &teedev->def_ctx simply ignored. So once opened,
>> &teedev->def_ctx will always remain open until the tee_device is alive.
>>
>>> We could initialize teedev->def_ctx on the first call to teedev_open()
>>> on that tee_device. We need a way to tell the
>>> teedev->desc->ops->open() to the backed driver that it's initializing
>>> the default context though, or optee_open() can't handle the
>>> tee-supplicant case properly.
>>>
>>
>> That's a good point. This way, it is guaranteed that there is one def_ctx
>> per teedev. There should be a way to tell the open() callback that it is
>> a def_ctx, so it is not registered as a supplicant context.
>>
>>
>>> Should we allow this function to be called more than once for each teedev?
>>
>> Yes, moving to teedev_open() will fix the issue.
>>
>>> Do we need serialization in this function if it's called after the
>>> driver is probed?
>>>
>>
>> True. I'll make sure there is no race.
>>
>>>>
>>>> -static void teedev_ctx_release(struct kref *ref)
>>>> -{
>>>> - struct tee_context *ctx = container_of(ref, struct tee_context,
>>>> - refcount);
>>>> - ctx->releasing = true;
>>>> - ctx->teedev->desc->ops->release(ctx);
>>>> - kfree(ctx);
>>>> + return ctx;
>>>> }
>>>> +EXPORT_SYMBOL_GPL(teedev_get_def_context);
>>>>
>>>> -void teedev_ctx_put(struct tee_context *ctx)
>>>> +void teedev_close_context(struct tee_context *ctx)
>>>> {
>>>> - if (ctx->releasing)
>>>> + struct tee_device *teedev = ctx->teedev;
>>>> + struct tee_shm *shm;
>>>> +
>>>> + if (ctx == &teedev->def_ctx)
>>>> return;
>>>>
>>>> - kref_put(&ctx->refcount, teedev_ctx_release);
>>>> -}
>>>> + teedev->desc->ops->release(ctx);
>>>>
>>>> -void teedev_close_context(struct tee_context *ctx)
>>>> -{
>>>> - struct tee_device *teedev = ctx->teedev;
>>>> + mutex_lock(&teedev->mutex);
>>>> + list_for_each_entry(shm, &ctx->list_shm, link) {
>>>> + /* Context released. However, shm still holding a teedev reference.
>>>> + * Replace shm->ctx with the default context so that tee_shm_get_from_id()
>>>> + * fails (i.e. it is not accessible from userspace) but shm still
>>>> + * holds a valid context for further clean up, e.g. shm_unregister().
>>>> + */
>>>
>>> /*
>>> * Please format
>>> * multiline comments
>>> * like this. Please
>>> * keep the lines at
>>> * max 80 columns
>>> * here and at other
>>> * places in the patch-
>>> * set.
>>> */
>>>
>>
>> Ack.
>>
>>>> + shm->ctx = &teedev->def_ctx;
>>>
>>> shm->ctx will always point to a valid context, even if it is the
>>> default context. It seems that we can always get hold of the correct
>>> teedev via shm->ctx->teedev. Do we need "tee: revert removal of
>>> redundant teedev in struct tee_shm"?
>>>
>>
>> It was there in case we wanted to use NULL, but with def_ctx, it is not
>> necessary. I am withdrawing that commit. :).
>>
>>> Shouldn't the shm be removed from the ctx->list_shm and be moved to
>>> teedev->def_ctx.list_shm?
>
> +1
>
Ack.
>>>
>>
>> Not really. If we put shm in the teedev->def_ctx.list_shm, by the time
>> we are closing the def_ctx, the list is guaranteed to be empty.
>>
>> However, I understand it is cleaner and more consistent to do that rather
>> than making changes to tee_shm_put().
>>
>> I'll do it.
>>
>>>> + }
>>>> + mutex_unlock(&teedev->mutex);
>>>>
>>>> - teedev_ctx_put(ctx);
>>>> + kfree(ctx);
>>>> tee_device_put(teedev);
>>>> }
>>>> EXPORT_SYMBOL_GPL(teedev_close_context);
>>>> @@ -946,6 +952,8 @@ struct tee_device *tee_device_alloc(const struct tee_desc *teedesc,
>>>>
>>>> teedev->desc = teedesc;
>>>> teedev->pool = pool;
>>>> + /* Only open default context when teedev_get_def_context() called. */
>>>> + teedev->def_ctx.teedev = NULL;
>
> Why don't you open the device context here only? This will associate
> it automatically with teedev lifespan and then
> teedev_get_def_context() will just return a reference to that.
>
> -Sumit
>
So my assumption is that the tee_devic_alloc() is called as part of
the driver initialization; there is no guarantee that at this time the
driver is actually ready to accept any open() callback.
Best Regards,
Amir
>>>>
>>>> return teedev;
>>>> err_devt:
>>>> @@ -1027,16 +1035,31 @@ EXPORT_SYMBOL_GPL(tee_device_register);
>>>>
>>>> void tee_device_put(struct tee_device *teedev)
>>>> {
>>>> - mutex_lock(&teedev->mutex);
>>>> - /* Shouldn't put in this state */
>>>> - if (!WARN_ON(!teedev->desc)) {
>>>> - teedev->num_users--;
>>>> - if (!teedev->num_users) {
>>>> - teedev->desc = NULL;
>>>> - complete(&teedev->c_no_users);
>>>> - }
>>>> + const struct tee_desc *desc;
>>>> +
>>>> + scoped_guard(mutex, &teedev->mutex) {
>>>> + desc = teedev->desc;
>>>> +
>>>> + /* Shouldn't put in this state */
>>>> + if (WARN_ON(!desc))
>>>> + return;
>>>> +
>>>> + /* If there is still users for teedev */
>>>> + if (--teedev->num_users)
>>>
>>> Please do teedev->num_users-- first and then check. It makes the code
>>> easier to read.
>>
>> Ack.
>>
>>>
>>>> + return;
>>>> +
>>>> + /* tee_device_unregister() has been called and there is no
>>>> + * user in userspace or kernel, including orphan shm for teedev.
>>>> + * Set teedev->desc to NULL, so that teedev can not be reused.
>>>> + */
>>>> + teedev->desc = NULL;
>>>> }
>>>> - mutex_unlock(&teedev->mutex);
>>>> +
>>>> + /* Release the default context */
>>>> + desc->ops->release(&teedev->def_ctx);
>>>
>>> This should only be done if teedev->def_ctx has been initialized.
>>>
>>
>> Ack.
>>
>>> Cheers,
>>> Jens
>>
>> Thank you very much for your comments :).
>> If you're okay with introducing def_ctx, I'll prepare a complete patchset
>> with all the details.
>>
>> Best Regards,
>> Amir
>>
>>
>>>
>>>> + teedev->def_ctx.teedev = NULL;
>>>> +
>>>> + complete(&teedev->c_no_users);
>>>> }
>>>>
>>>> bool tee_device_get(struct tee_device *teedev)
>>>> diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
>>>> index 9bc50605227c..6c7bcc308958 100644
>>>> --- a/drivers/tee/tee_private.h
>>>> +++ b/drivers/tee/tee_private.h
>>>> @@ -17,9 +17,6 @@ int tee_shm_get_fd(struct tee_shm *shm);
>>>> bool tee_device_get(struct tee_device *teedev);
>>>> void tee_device_put(struct tee_device *teedev);
>>>>
>>>> -void teedev_ctx_get(struct tee_context *ctx);
>>>> -void teedev_ctx_put(struct tee_context *ctx);
>>>> -
>>>> struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
>>>> struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>>>> unsigned long addr, size_t length);
>>>> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
>>>> index c0164c0f4a01..f07274291edf 100644
>>>> --- a/drivers/tee/tee_shm.c
>>>> +++ b/drivers/tee/tee_shm.c
>>>> @@ -59,8 +59,6 @@ static void tee_shm_release(struct tee_shm *shm)
>>>> release_registered_pages(shm);
>>>> }
>>>>
>>>> - teedev_ctx_put(shm->ctx);
>>>> -
>>>> kfree(shm);
>>>>
>>>> tee_device_put(teedev);
>>>> @@ -93,13 +91,6 @@ static struct tee_shm *shm_alloc_helper(struct tee_context *ctx, size_t size,
>>>> shm->flags = flags;
>>>> shm->teedev = teedev;
>>>> shm->id = id;
>>>> -
>>>> - /*
>>>> - * We're assigning this as it is needed if the shm is to be
>>>> - * registered. If this function returns OK then the caller expected
>>>> - * to call teedev_ctx_get() or clear shm->ctx in case it's not
>>>> - * needed any longer.
>>>> - */
>>>> shm->ctx = ctx;
>>>>
>>>> rc = teedev->pool->ops->alloc(teedev->pool, shm, size, align);
>>>> @@ -112,7 +103,6 @@ static struct tee_shm *shm_alloc_helper(struct tee_context *ctx, size_t size,
>>>> list_add_tail(&shm->link, &ctx->list_shm);
>>>> mutex_unlock(&teedev->mutex);
>>>>
>>>> - teedev_ctx_get(ctx);
>>>> return shm;
>>>> err_kfree:
>>>> kfree(shm);
>>>> @@ -295,12 +285,10 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
>>>> goto err_dev_put;
>>>> }
>>>>
>>>> - teedev_ctx_get(ctx);
>>>> -
>>>> shm = kzalloc(sizeof(*shm), GFP_KERNEL);
>>>> if (!shm) {
>>>> ret = ERR_PTR(-ENOMEM);
>>>> - goto err_ctx_put;
>>>> + goto err_dev_put;
>>>> }
>>>>
>>>> refcount_set(&shm->refcount, 1);
>>>> @@ -313,7 +301,7 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
>>>> num_pages = iov_iter_npages(iter, INT_MAX);
>>>> if (!num_pages) {
>>>> ret = ERR_PTR(-ENOMEM);
>>>> - goto err_ctx_put;
>>>> + goto err_dev_put;
>>>> }
>>>>
>>>> shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
>>>> @@ -361,8 +349,6 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
>>>> kfree(shm->pages);
>>>> err_free_shm:
>>>> kfree(shm);
>>>> -err_ctx_put:
>>>> - teedev_ctx_put(ctx);
>>>> err_dev_put:
>>>> tee_device_put(teedev);
>>>> return ret;
>>>> diff --git a/include/linux/tee_core.h b/include/linux/tee_core.h
>>>> index a38494d6b5f4..13393ddac530 100644
>>>> --- a/include/linux/tee_core.h
>>>> +++ b/include/linux/tee_core.h
>>>> @@ -44,6 +44,7 @@
>>>> * @idr: register of user space shared memory objects allocated or
>>>> * registered on this device
>>>> * @pool: shared memory pool
>>>> + * @def_ctx: default context used if there is no context available, e.g. internal driver calls.
>>>> */
>>>> struct tee_device {
>>>> char name[TEE_MAX_DEV_NAME_LEN];
>>>> @@ -60,6 +61,7 @@ struct tee_device {
>>>>
>>>> struct idr idr;
>>>> struct tee_shm_pool *pool;
>>>> + struct tee_context def_ctx;
>>>> };
>>>>
>>>> /**
>>>> @@ -309,6 +311,19 @@ static inline bool tee_param_is_memref(struct tee_param *param)
>>>> */
>>>> struct tee_context *teedev_open(struct tee_device *teedev);
>>>>
>>>> +/**
>>>> + * teedev_get_def_context() - Get default context for a struct tee_device
>>>> + * @teedev: Device to open
>>>> + *
>>>> + * Unlike a context that returned from teedev_open(), the default context is static
>>>> + * and available as long as @teedev has a user ''other then this context''. This context
>>>> + * can be used for driver internal operation and clean up where a context should be
>>>> + * available, while tee_device_unregister() is waiting for other users to go away.
>>>> + *
>>>> + * @return a pointer to struct tee_context on success or an ERR_PTR on failure.
>>>> + */
>>>> +struct tee_context *teedev_get_def_context(struct tee_device *teedev);
>>>> +
>>>> /**
>>>> * teedev_close_context() - closes a struct tee_context
>>>> * @ctx: The struct tee_context to close
>>>> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
>>>> index 1b57cddfecc8..9633e14ba484 100644
>>>> --- a/include/linux/tee_drv.h
>>>> +++ b/include/linux/tee_drv.h
>>>> @@ -7,7 +7,6 @@
>>>> #define __TEE_DRV_H
>>>>
>>>> #include <linux/device.h>
>>>> -#include <linux/kref.h>
>>>> #include <linux/list.h>
>>>> #include <linux/mod_devicetable.h>
>>>> #include <linux/tee.h>
>>>> @@ -25,10 +24,6 @@ struct tee_device;
>>>> * @teedev: pointer to this drivers struct tee_device
>>>> * @list_shm: List of shared memory object owned by this context
>>>> * @data: driver specific context data, managed by the driver
>>>> - * @refcount: reference counter for this structure
>>>> - * @releasing: flag that indicates if context is being released right now.
>>>> - * It is needed to break circular dependency on context during
>>>> - * shared memory release.
>>>> * @supp_nowait: flag that indicates that requests in this context should not
>>>> * wait for tee-supplicant daemon to be started if not present
>>>> * and just return with an error code. It is needed for requests
>>>> @@ -41,8 +36,6 @@ struct tee_context {
>>>> struct tee_device *teedev;
>>>> struct list_head list_shm;
>>>> void *data;
>>>> - struct kref refcount;
>>>> - bool releasing;
>>>> bool supp_nowait;
>>>> bool cap_memref_null;
>>>> };
>>>>
>>>> --
>>>> 2.34.1
>>>>
