On Thu, 26 Oct 2023 at 16:06, Jens Wiklander jens.wiklander@linaro.org wrote:
On Thu, Oct 26, 2023 at 11:36 AM Sumit Garg sumit.garg@linaro.org wrote:
On Fri, 20 Oct 2023 at 19:29, Balint Dobszay balint.dobszay@arm.com wrote:
On 19 Oct 2023, at 16:16, Jens Wiklander wrote:
On Tue, Oct 17, 2023 at 1:14 PM Sumit Garg sumit.garg@linaro.org wrote:
On Mon, 16 Oct 2023 at 13:27, Jens Wiklander jens.wiklander@linaro.org wrote:
On Fri, Oct 13, 2023 at 1:38 PM Sumit Garg sumit.garg@linaro.org wrote: > On Tue, 10 Oct 2023 at 21:11, Balint Dobszay balint.dobszay@arm.com wrote: >> On 3 Oct 2023, at 17:42, Sumit Garg wrote: >>> On Wed, 27 Sept 2023 at 20:56, Balint Dobszay balint.dobszay@arm.com wrote:
[snip]
>>>> +static int tstee_invoke_func(struct tee_context *ctx, struct tee_ioctl_invoke_arg *arg, >>>> + struct tee_param *param) >>>> +{ >>>> + struct tstee *tstee = tee_get_drvdata(ctx->teedev); >>>> + struct ffa_device *ffa_dev = tstee->ffa_dev; >>>> + struct ts_context_data *ctxdata = ctx->data; >>>> + struct ffa_send_direct_data ffa_data; >>>> + struct tee_shm *shm = NULL; >>>> + struct ts_session *sess; >>>> + u32 req_len, ffa_args[5] = {}; >>>> + int shm_id, rc; >>>> + u8 iface_id; >>>> + u64 handle; >>>> + u16 opcode; >>>> + >>>> + mutex_lock(&ctxdata->mutex); >>>> + sess = find_session(ctxdata, arg->session); >>>> + >>>> + /* Do this while holding the mutex to make sure that the session wasn't closed meanwhile */ >>>> + if (sess) >>>> + iface_id = sess->iface_id; >>>> + >>>> + mutex_unlock(&ctxdata->mutex); >>>> + if (!sess) >>>> + return -EINVAL; >>>> + >>>> + opcode = lower_16_bits(arg->func); >>>> + shm_id = lower_32_bits(param[0].u.value.a); >>>> + req_len = lower_32_bits(param[0].u.value.b); >>>> + >>>> + if (shm_id != 0) { >>>> + shm = tee_shm_get_from_id(ctx, shm_id); >>>> + if (IS_ERR(shm)) >>>> + return PTR_ERR(shm); >>>> + >>>> + if (shm->size < req_len) { >>>> + pr_err("request doesn't fit into shared memory buffer\n"); >>>> + rc = -EINVAL; >>>> + goto out; >>>> + } >>>> + >>>> + handle = shm->sec_world_id; >>>> + } else { >>>> + handle = FFA_INVALID_MEM_HANDLE; >>>> + } >>>> + >>>> + ffa_args[TS_RPC_CTRL_REG] = TS_RPC_CTRL_PACK_IFACE_OPCODE(iface_id, opcode); >>>> + ffa_args[TS_RPC_SERVICE_MEM_HANDLE_LSW] = lower_32_bits(handle); >>>> + ffa_args[TS_RPC_SERVICE_MEM_HANDLE_MSW] = upper_32_bits(handle); >>>> + ffa_args[TS_RPC_SERVICE_REQ_LEN] = req_len; >>>> + ffa_args[TS_RPC_SERVICE_CLIENT_ID] = 0; >>>> + >>>> + arg_list_to_ffa_data(ffa_args, &ffa_data); >>>> + rc = ffa_dev->ops->msg_ops->sync_send_receive(ffa_dev, &ffa_data); >>> >>> I haven't dug deeper into the ABI yet, which is something I will look >>> into. But these RPC commands caught my attention. Are these RPC calls >>> blocking in nature? Is there a possibility that these could cause CPU >>> stalls? Do the Linux interrupts remain unhandled until the RPC calls >>> return? >> >> Yes, that is correct. We did encounter CPU stalls indeed, our solution >> was to enable preemption of S-EL0 SPs in OP-TEE [3] which solved the >> issue. > > I would have preferred to unite FFA_INTERRUPT and > OPTEE_FFA_YIELDING_CALL_RETURN_INTERRUPT since underneath both are > using FFA ABI. > > Jens, > > Can we change OP-TEE to use FFA_INTERRUPT as well when using FFA ABI?
No, OP-TEE uses managed exit. Among other advantages, it allows resuming execution on a different CPU.
I suppose that should be the case with FFA_INTERRUPT too. OP-TEE should be able to resume SPs on different CPUs as well, right?
Possibly, but I leave that to Balint and company to sort out if that's desired or not.
FF-A mandates that S-EL0 SPs have a single execution context, run only on a single PE in the system at any point of time and are capable of migrating. Also, FF-A allows resuming a S-EL0 SP on a different CPU after it gets preempted by a NS interrupt. I think OP-TEE as S-EL1 SPMC does support this, but I don't have a setup yet that would explicitly test this scenario.
You can try to add a few minutes loop within a secure partition and see if the Linux scheduler reschedules on a different CPUs. I suppose you need to keep the system loaded with other normal world apps too.
Managed exit is only available for S-EL1 SPs.
So does that mean OP-TEE can use FF-A constructs like (FFA_INTERRUPT) for managed exit instead of custom OPTEE_FFA_YIELDING_CALL_RETURN_INTERRUPT?
No, and to be clear OPTEE_FFA_YIELDING_CALL_RETURN_INTERRUPT isn't a custom solution, it's fully within the specification.
I am not talking about it being out of specification. It's rather that if the base FF-A layer provides you with a feature then we shouldn't need to reimplement in every SP (OP-TEE or other trusted OS) communication stack.
Returning via FFA_INTERRUPT is a simplified model where the SP has less control over the CPU.
I would like to understand which exact bits you are referring to. From Linux point of view, I don't see any difference.
I imagine that it wouldn't play very nicely with spinlocks.
Aren't interrupts disabled while spinlock is being held?
-Sumit
Cheers, Jens
-Sumit