Messages in this thread | | | From | Etienne Carriere <> | Date | Thu, 9 Feb 2023 10:11:56 +0100 | Subject | Re: [PATCH 1/2] tee: system invocation |
| |
On Thu, 9 Feb 2023 at 09:11, Etienne Carriere <etienne.carriere@linaro.org> wrote: > > Hi Jens, > > > On Thu, 9 Feb 2023 at 08:14, Jens Wiklander <jens.wiklander@linaro.org> wrote: > > > > Hi Etienne, > > > > On Wed, Feb 08, 2023 at 06:09:17PM +0100, Etienne Carriere wrote: > > > Hello Sumit, Jens, > > > > > [snip] > > > > > > > > > > > > > > > > if (rpc_arg && tee_shm_is_dynamic(shm)) { > > > > > > > > - param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG; > > > > > > > > + if (ctx->sys_service && > > > > > > > > + (optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD)) > > > > > > > > + param.a0 = OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG; > > > > > > > > + else > > > > > > > > + param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG; > > > > > > > > > > > > > > This system thread flag should also be applicable to platforms without > > > > > > > registered arguments support. IOW, we need similar equivalents for > > > > > > > OPTEE_SMC_FUNCID_CALL_WITH_ARG and OPTEE_SMC_FUNCID_CALL_WITH_RPC_ARG > > > > > > > too. So I would rather suggest that we add following flag to all 3 > > > > > > > call types: > > > > > > > > > > > > > > #define OPTEE_SMC_CALL_SYSTEM_THREAD_FLAG 0x8000 > > > > > > > > > > > > The main reason platforms don't support registered arguments is that > > > > > > they haven't been updated since this was introduced. So if a platform > > > > > > needs system threads it could update to use registered arguments too. > > > > > > > > > > Are we hinting at deprecating reserved shared memory support? If yes, > > > > > wouldn't it be better to be explicit about it with a boot time warning > > > > > message about its deprecation? > > > > > > > > > > Otherwise it will be difficult to debug for the end user to find out > > > > > why system thread support isn't activated. > > > > > > > > > > > The Linux kernel already supports registered arguments. An advantage > > > > > > with the current approach is that the ABI is easier to implement > > > > > > since we have distinct SMC IDs for each function. > > > > > > > > > > I see your point but my initial thought was that we don't end up > > > > > making that list too large that it becomes cumbersome to maintain, > > > > > involving all the combinatorial. > > > > > > > > You have a point. Etienne, do you think we could give it a try at > > > > https://github.com/OP-TEE/optee_os/pull/5789 to better see how this > > > > would play out? > > > > > > > > > > Indeed I miss that... > > > With the patch proposed here, indeed if OP-TEE does not support > > > dynamic shared memory then Linux will never use the provisioned TEE > > > thread. This is weird as in such a case OP-TEE provisions resources > > > that will never be used, which is the exact opposite goal of this > > > feature. Verified on our qemu-arm setup. > > > > > > For simplicity, I think this system invocation should require OP-TEE > > > supports dyn shm. > > > > It's not obvious to me that this will easier to implement and maintain. > > Looking at the code in optee_os it looks like using a flag bit as > > proposed by Sumit would be quite easy to handle. > > OP-TEE could auto disable thread provis when dyn shm is disabled, right.
By the way, from OP-TEE OS, we have config switches for dyn-shm and system context provisioning. The latter could depend on the former so it's clear at build time when TEE can embed the capability.
Br, etienne
> Will it be sufficient? We will still face cases where an OP-TEE > provisions thread but Linux kernel is not aware (older vanilla kernel > used with a recent OP-TEE OS). Not much platforms are really affected > I guess but those executing with pager in small RAMs where a 4kB > thread context costs. > > (snip)
| |