Messages in this thread | | | From | Etienne CARRIERE - foss <> | Subject | Re: [PATCH v10 3/4] tee: optee: support tracking system threads | Date | Wed, 11 Oct 2023 07:11:28 +0000 |
| |
> From: Sumit Garg <sumit.garg@linaro.org> > Sent: Friday, October 6, 2023 11:33 AM > > On Tue, 3 Oct 2023 at 19:36, Etienne Carriere > <etienne.carriere@foss.st.com> wrote: > > > > Adds support in the OP-TEE driver to keep track of reserved system > > threads. The logic allows one OP-TEE thread to be reserved to TEE system > > sessions. > > > > The optee_cq_*() functions are updated to handle this if enabled, > > that is when TEE describes how many thread context it supports > > and when at least 1 session has registered as a system session > > (using tee_client_system_session()). > > > > For sake of simplicity, initialization of call queue management > > is factorized into new helper function optee_cq_init(). > > > > The SMC ABI part of the driver enables this tracking, but the > > FF-A ABI part does not. > > > > > > Co-developed-by: Jens Wiklander <jens.wiklander@linaro.org> > > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org> > > Co-developed-by: Sumit Garg <sumit.garg@linaro.org> > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com> > > --- > > Changes since v9: > > - Add a reference counter for TEE system thread provisioning. We reserve > > a TEE thread context for system session only when there is at least > > 1 opened system session. > > - Use 2 wait queue lists, normal_waiters and sys_waiter, as proposed in > > patch v8. Using a single list can prevent a waiting system thread from > > being resumed if the executing system thread wakes a normal waiter in > > the list. > > How would that be possible? The system thread wakeup > (free_thread_threshold = 0) is given priority over normal thread > wakeup (free_thread_threshold = 1). I think a single queue list would > be sufficient as demonstrated in v9. >
Hello Sumit,
I think a system session can be trapped waiting when using a single queue list. To have a chance to reach the TEE, a waiting thread must wait that a TEE thread comes out of the TEE and calls complete() on the waitqueue to wake next waiter.
To illustrate, consider a 10 TEE threads configuration on TEE side (::total_thread_count=10 at init), and several TEE clients in Linux OS, including 2 system sessions, from 2 consumer drivers (::sys_thread_req_count=2).
Imagine the 9 normal threads and the 1 system thread are in use. (::free_thread_count=0), Now comes the other system session: it goes to the waitqueue list. Now comes a normal session invocation: it goes to the waitqueue list, 1st position.
Now, TEE system thread returns to Linux: It increments the counter, ::free_thread_count=1, and calls complete() for the waitequeue. The 1st element in the waitqueue list is the last entered normal session invocation. However, that waiter won't switch local boolean 'need_wait' to false because ::free_thread_count=1 and ::sys_thread_req_count!=0. So no attempt to reach TEE and wake another waiter on return. At that point there is a system session in the waitqueue list that could enter TEE (::free_thread_count=1) but is waiting someone returns from the TEE.
With 2 lists, we first treat system sessions to overcome that. Am I missing something?
Best regards, Etienne
> -Sumit > > > - Updated my e-mail address. > > - Rephrased a bit the commit message. > > > > Changes since patch v8 > > - Patch v9 (reference below) attempted to simplify the implementation > > https://lore.kernel.org/lkml/20230517143311.585080-1-sumit.garg@linaro.org/#t > > > > Changes since v7: > > - Changes the logic to reserve at most 1 call entry for system sessions > > as per patches v6 and v7 discussion threads (the 2 below bullets) > > and updates commit message accordingly. > > - Field optee_call_queue::res_sys_thread_count is replaced with 2 fields: > > sys_thread_req_count and boolean sys_thread_in_use. > > - Field optee_call_waiter::sys_thread is replaced with 2 fields: > > sys_thread_req and sys_thread_used. > > - Adds inline description comments for struct optee_call_queue and > > struct optee_call_waiter. > > > > Changes since v6: > > - Moved out changes related to adding boolean system thread attribute > > into optee driver call queue and SMC/FF-A ABIs API functions. These > > changes were squashed into patch 1/4 of this patch v7 series. > > - Comment about adding a specific commit for call queue refactoring > > was not addressed such a patch would only introduce function > > optee_cq_init() with very little content in (mutex & list init). > > - Added Co-developed-by tag for Jens contribution as he's not responsible > > for the changes I made in this patch v7. > > > > No change since v5 > > > > Changes since v4: > > - New change that supersedes implementation proposed in PATCH v4 > > (tee: system invocation"). Thanks to Jens implementation we don't need > > the new OP-TEE services that my previous patch versions introduced to > > monitor system threads entry. Now, Linux optee SMC ABI driver gets TEE > > provisioned thread contexts count once and monitors thread entries in > > OP-TEE on that basis and the system thread capability of the related > > tee session. By the way, I dropped the WARN_ONCE() call I suggested > > on tee thread exhaustion as it does not provides useful information. > > --- > > drivers/tee/optee/call.c | 128 ++++++++++++++++++++++++++++-- > > drivers/tee/optee/ffa_abi.c | 3 +- > > drivers/tee/optee/optee_private.h | 24 +++++- > > drivers/tee/optee/smc_abi.c | 16 +++- > > 4 files changed, 159 insertions(+), 12 deletions(-) > > > > diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c > > index 152ae9bb1785..38543538d77b 100644 > > --- a/drivers/tee/optee/call.c > > +++ b/drivers/tee/optee/call.c > > @@ -39,9 +39,31 @@ struct optee_shm_arg_entry { > > DECLARE_BITMAP(map, MAX_ARG_COUNT_PER_ENTRY); > > }; > > > > +void optee_cq_init(struct optee_call_queue *cq, int thread_count) > > +{ > > + mutex_init(&cq->mutex); > > + INIT_LIST_HEAD(&cq->sys_waiters); > > + INIT_LIST_HEAD(&cq->normal_waiters); > > + > > + /* > > + * If cq->total_thread_count is 0 then we're not trying to keep > > + * track of how many free threads we have, instead we're relying on > > + * the secure world to tell us when we're out of thread and have to > > + * wait for another thread to become available. > > + */ > > + cq->total_thread_count = thread_count; > > + cq->free_thread_count = thread_count; > > +} > > + > > void optee_cq_wait_init(struct optee_call_queue *cq, > > struct optee_call_waiter *w, bool sys_thread) > > { > > + unsigned int free_thread_threshold; > > + bool need_wait = false; > > + > > + memset(w, 0, sizeof(*w)); > > + w->sys_thread = sys_thread; > > + > > /* > > * We're preparing to make a call to secure world. In case we can't > > * allocate a thread in secure world we'll end up waiting in > > @@ -53,15 +75,47 @@ void optee_cq_wait_init(struct optee_call_queue *cq, > > mutex_lock(&cq->mutex); > > > > /* > > - * We add ourselves to the queue, but we don't wait. This > > - * guarantees that we don't lose a completion if secure world > > - * returns busy and another thread just exited and try to complete > > - * someone. > > + * We add ourselves to a queue, but we don't wait. This guarantees > > + * that we don't lose a completion if secure world returns busy and > > + * another thread just exited and try to complete someone. > > */ > > init_completion(&w->c); > > - list_add_tail(&w->list_node, &cq->waiters); > > + > > + if (sys_thread) > > + list_add_tail(&w->list_node, &cq->sys_waiters); > > + else > > + list_add_tail(&w->list_node, &cq->normal_waiters); > > + > > + if (cq->total_thread_count) { > > + if (sys_thread || !cq->sys_thread_req_count) > > + free_thread_threshold = 0; > > + else > > + free_thread_threshold = 1; > > + > > + if (cq->free_thread_count > free_thread_threshold) > > + cq->free_thread_count--; > > + else > > + need_wait = true; > > + } > > > > mutex_unlock(&cq->mutex); > > + > > + while (need_wait) { > > + optee_cq_wait_for_completion(cq, w); > > + mutex_lock(&cq->mutex); > > + > > + if (sys_thread || !cq->sys_thread_req_count) > > + free_thread_threshold = 0; > > + else > > + free_thread_threshold = 1; > > + > > + if (cq->free_thread_count > free_thread_threshold) { > > + cq->free_thread_count--; > > + need_wait = false; > > + } > > + > > + mutex_unlock(&cq->mutex); > > + } > > } > > > > void optee_cq_wait_for_completion(struct optee_call_queue *cq, > > @@ -74,7 +128,11 @@ void optee_cq_wait_for_completion(struct optee_call_queue *cq, > > /* Move to end of list to get out of the way for other waiters */ > > list_del(&w->list_node); > > reinit_completion(&w->c); > > - list_add_tail(&w->list_node, &cq->waiters); > > + > > + if (w->sys_thread) > > + list_add_tail(&w->list_node, &cq->sys_waiters); > > + else > > + list_add_tail(&w->list_node, &cq->normal_waiters); > > > > mutex_unlock(&cq->mutex); > > } > > @@ -83,7 +141,15 @@ static void optee_cq_complete_one(struct optee_call_queue *cq) > > { > > struct optee_call_waiter *w; > > > > - list_for_each_entry(w, &cq->waiters, list_node) { > > + /* Wake waiting system session first */ > > + list_for_each_entry(w, &cq->sys_waiters, list_node) { > > + if (!completion_done(&w->c)) { > > + complete(&w->c); > > + break; > > + } > > + } > > + > > + list_for_each_entry(w, &cq->normal_waiters, list_node) { > > if (!completion_done(&w->c)) { > > complete(&w->c); > > break; > > @@ -104,6 +170,8 @@ void optee_cq_wait_final(struct optee_call_queue *cq, > > /* Get out of the list */ > > list_del(&w->list_node); > > > > + cq->free_thread_count++; > > + > > /* Wake up one eventual waiting task */ > > optee_cq_complete_one(cq); > > > > @@ -119,6 +187,28 @@ void optee_cq_wait_final(struct optee_call_queue *cq, > > mutex_unlock(&cq->mutex); > > } > > > > +/* Count registered system sessions to reserved a system thread or not */ > > +static bool optee_cq_incr_sys_thread_count(struct optee_call_queue *cq) > > +{ > > + if (cq->total_thread_count <= 1) > > + return false; > > + > > + mutex_lock(&cq->mutex); > > + cq->sys_thread_req_count++; > > + mutex_unlock(&cq->mutex); > > + > > + return true; > > +} > > + > > +static void optee_cq_decr_sys_thread_count(struct optee_call_queue *cq) > > +{ > > + mutex_lock(&cq->mutex); > > + cq->sys_thread_req_count--; > > + /* If there's someone waiting, let it resume */ > > + optee_cq_complete_one(cq); > > + mutex_unlock(&cq->mutex); > > +} > > + > > /* Requires the filpstate mutex to be held */ > > static struct optee_session *find_session(struct optee_context_data *ctxdata, > > u32 session_id) > > @@ -361,6 +451,27 @@ int optee_open_session(struct tee_context *ctx, > > return rc; > > } > > > > +int optee_system_session(struct tee_context *ctx, u32 session) > > +{ > > + struct optee *optee = tee_get_drvdata(ctx->teedev); > > + struct optee_context_data *ctxdata = ctx->data; > > + struct optee_session *sess; > > + int rc = -EINVAL; > > + > > + mutex_lock(&ctxdata->mutex); > > + > > + sess = find_session(ctxdata, session); > > + if (sess && (sess->use_sys_thread || > > + optee_cq_incr_sys_thread_count(&optee->call_queue))) { > > + sess->use_sys_thread = true; > > + rc = 0; > > + } > > + > > + mutex_unlock(&ctxdata->mutex); > > + > > + return rc; > > +} > > + > > int optee_close_session_helper(struct tee_context *ctx, u32 session, > > bool system_thread) > > { > > @@ -380,6 +491,9 @@ int optee_close_session_helper(struct tee_context *ctx, u32 session, > > > > optee_free_msg_arg(ctx, entry, offs); > > > > + if (system_thread) > > + optee_cq_decr_sys_thread_count(&optee->call_queue); > > + > > return 0; > > } > > > > diff --git a/drivers/tee/optee/ffa_abi.c b/drivers/tee/optee/ffa_abi.c > > index 5fde9d4100e3..0c9055691343 100644 > > --- a/drivers/tee/optee/ffa_abi.c > > +++ b/drivers/tee/optee/ffa_abi.c > > @@ -852,8 +852,7 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev) > > if (rc) > > goto err_unreg_supp_teedev; > > mutex_init(&optee->ffa.mutex); > > - mutex_init(&optee->call_queue.mutex); > > - INIT_LIST_HEAD(&optee->call_queue.waiters); > > + optee_cq_init(&optee->call_queue, 0); > > optee_supp_init(&optee->supp); > > optee_shm_arg_cache_init(optee, arg_cache_flags); > > ffa_dev_set_drvdata(ffa_dev, optee); > > diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h > > index b68273051454..69f6397c3646 100644 > > --- a/drivers/tee/optee/optee_private.h > > +++ b/drivers/tee/optee/optee_private.h > > @@ -40,15 +40,35 @@ typedef void (optee_invoke_fn)(unsigned long, unsigned long, unsigned long, > > unsigned long, unsigned long, > > struct arm_smccc_res *); > > > > +/* > > + * struct optee_call_waiter - TEE entry may need to wait for a free TEE thread > > + * @list_node Reference in waiters list > > + * @c Waiting completion reference > > + * @sys_thread_req True if waiter belongs to a system thread > > + */ > > struct optee_call_waiter { > > struct list_head list_node; > > struct completion c; > > + bool sys_thread; > > }; > > > > +/* > > + * struct optee_call_queue - OP-TEE call queue management > > + * @mutex Serializes access to this struct > > + * @sys_waiters List of system threads waiting to enter OP-TEE > > + * @normal_waiters List of normal threads waiting to enter OP-TEE > > + * @total_thread_count Overall number of thread context in OP-TEE or 0 > > + * @free_thread_count Number of threads context free in OP-TEE > > + * @sys_thread_req_count Number of registered system thread sessions > > + */ > > struct optee_call_queue { > > /* Serializes access to this struct */ > > struct mutex mutex; > > - struct list_head waiters; > > + struct list_head sys_waiters; > > + struct list_head normal_waiters; > > + int total_thread_count; > > + int free_thread_count; > > + int sys_thread_req_count; > > }; > > > > struct optee_notif { > > @@ -254,6 +274,7 @@ int optee_supp_send(struct tee_context *ctx, u32 ret, u32 num_params, > > int optee_open_session(struct tee_context *ctx, > > struct tee_ioctl_open_session_arg *arg, > > struct tee_param *param); > > +int optee_system_session(struct tee_context *ctx, u32 session); > > int optee_close_session_helper(struct tee_context *ctx, u32 session, > > bool system_thread); > > int optee_close_session(struct tee_context *ctx, u32 session); > > @@ -303,6 +324,7 @@ static inline void optee_to_msg_param_value(struct optee_msg_param *mp, > > mp->u.value.c = p->u.value.c; > > } > > > > +void optee_cq_init(struct optee_call_queue *cq, int thread_count); > > void optee_cq_wait_init(struct optee_call_queue *cq, > > struct optee_call_waiter *w, bool sys_thread); > > void optee_cq_wait_for_completion(struct optee_call_queue *cq, > > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c > > index 1033d7da03ea..5595028d6dae 100644 > > --- a/drivers/tee/optee/smc_abi.c > > +++ b/drivers/tee/optee/smc_abi.c > > @@ -1211,6 +1211,7 @@ static const struct tee_driver_ops optee_clnt_ops = { > > .release = optee_release, > > .open_session = optee_open_session, > > .close_session = optee_close_session, > > + .system_session = optee_system_session, > > .invoke_func = optee_invoke_func, > > .cancel_req = optee_cancel_req, > > .shm_register = optee_shm_register, > > @@ -1358,6 +1359,16 @@ static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn, > > return true; > > } > > > > +static unsigned int optee_msg_get_thread_count(optee_invoke_fn *invoke_fn) > > +{ > > + struct arm_smccc_res res; > > + > > + invoke_fn(OPTEE_SMC_GET_THREAD_COUNT, 0, 0, 0, 0, 0, 0, 0, &res); > > + if (res.a0) > > + return 0; > > + return res.a1; > > +} > > + > > static struct tee_shm_pool * > > optee_config_shm_memremap(optee_invoke_fn *invoke_fn, void **memremaped_shm) > > { > > @@ -1610,6 +1621,7 @@ static int optee_probe(struct platform_device *pdev) > > struct optee *optee = NULL; > > void *memremaped_shm = NULL; > > unsigned int rpc_param_count; > > + unsigned int thread_count; > > struct tee_device *teedev; > > struct tee_context *ctx; > > u32 max_notif_value; > > @@ -1637,6 +1649,7 @@ static int optee_probe(struct platform_device *pdev) > > return -EINVAL; > > } > > > > + thread_count = optee_msg_get_thread_count(invoke_fn); > > if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps, > > &max_notif_value, > > &rpc_param_count)) { > > @@ -1726,8 +1739,7 @@ static int optee_probe(struct platform_device *pdev) > > if (rc) > > goto err_unreg_supp_teedev; > > > > - mutex_init(&optee->call_queue.mutex); > > - INIT_LIST_HEAD(&optee->call_queue.waiters); > > + optee_cq_init(&optee->call_queue, thread_count); > > optee_supp_init(&optee->supp); > > optee->smc.memremaped_shm = memremaped_shm; > > optee->pool = pool; > > -- > > 2.25.1 > > >
| |