On Thu, Mar 17, 2022 at 12:40 PM Sumit Garg sumit.garg@linaro.org wrote:
On Wed, 16 Mar 2022 at 13:47, Jens Wiklander jens.wiklander@linaro.org wrote:
[snip]
diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h index d44a6ae994f8..378741a459b6 100644 --- a/drivers/tee/optee/optee_smc.h +++ b/drivers/tee/optee/optee_smc.h @@ -107,14 +107,22 @@ struct optee_smc_call_get_os_revision_result { /*
- Call with struct optee_msg_arg as argument
- When calling this function normal world has a few responsibilities:
- When called with OPTEE_SMC_CALL_WITH_RPC_ARG or
- OPTEE_SMC_CALL_WITH_REGD_ARG in a0 there is one RPC struct optee_msg_arg
- following after the first struct optee_msg_arg. The RPC struct
- optee_msg_arg has reserved space for the number of RPC parameters as
- returned by OPTEE_SMC_EXCHANGE_CAPABILITIES.
- When calling these functions normal world has a few responsibilities:
- It must be able to handle eventual RPCs
- Non-secure interrupts should not be masked
- If asynchronous notifications has been negotiated successfully, then
- asynchronous notifications should be unmasked during this call.
- the interrupt for asynchronous notifications should be unmasked
- during this call.
- Call register usage:
- a0 SMC Function ID, OPTEE_SMC*CALL_WITH_ARG
- Call register usage, OPTEE_SMC_CALL_WITH_ARG and
- OPTEE_SMC_CALL_WITH_RPC_ARG:
- a0 SMC Function ID, OPTEE_SMC_CALL_WITH_ARG or OPTEE_SMC_CALL_WITH_RPC_ARG
- a1 Upper 32 bits of a 64-bit physical pointer to a struct optee_msg_arg
- a2 Lower 32 bits of a 64-bit physical pointer to a struct optee_msg_arg
- a3 Cache settings, not used if physical pointer is in a predefined shared
@@ -122,6 +130,15 @@ struct optee_smc_call_get_os_revision_result {
- a4-6 Not used
- a7 Hypervisor Client ID register
- Call register usage, OPTEE_SMC_CALL_WITH_REGD_ARG:
Although I didn't see any reference to OPTEE_SMC_CALL_WITH_REGD_ARG in the commit message, but do we really need to introduce it? Wouldn't it be possible to just pass additional "shared memory cookie" value as part of "Not used" (a4-6) arguments?
I'll update the commit message to mention OPTEE_SMC_CALL_WITH_REGD_ARG too. I think it's more clear with a separate ID for this, less risk of confusion.
IMO, it would unnecessarily complicate and introduce ambiguity in the ABI as after this patch we will have:
CALL_WITH_ARG: Standard arguments *without* pre-allocated RPC arguments buffer CALL_WITH_RPC_ARG: Standard arguments *with* pre-allocated RPC arguments buffer CALL_WITH_REGD_ARG: Registered arguments but *not* explicit whether RPC arguments buffer is there or not.
CALL_WITH_REGD_ARG is quite explicit in the description above (in the patch): * When called with OPTEE_SMC_CALL_WITH_RPC_ARG or * OPTEE_SMC_CALL_WITH_REGD_ARG in a0 there is one RPC struct optee_msg_arg * following after the first struct optee_msg_arg. The RPC struct * optee_msg_arg has reserved space for the number of RPC parameters as * returned by OPTEE_SMC_EXCHANGE_CAPABILITIES.
I chose to use two new SMC IDs to have one clear purpose for each.
I preferred the name OPTEE_SMC_CALL_WITH_REGD_ARG instead of OPTEE_SMC_CALL_WITH_REGD_RPC_ARG since I thought the former was long enough.
If we keep the ABI simplified to say we only support two types of invocation irrespective of whether the arguments are allocated from statically shared memory or dynamically shared memory:
CALL_WITH_ARG: Standard arguments *without* pre-allocated RPC arguments buffer CALL_WITH_RPC_ARG: Standard arguments *with* pre-allocated RPC arguments buffer
That's only simple on the surface. When looking into the details of CALL_WITH_RPC_ARG you'd need a more complicated register usage since the function would be doing two different things.
How would the callee know if it's the cookie or the physical address it should use? Whatever we do, we're extenting the ABI.
Isn't it possible for OP-TEE to determine if it's a valid cookie or not which will be passed into currently unused arguments?
Actually, we need three registers, one to pass the offset in too.
Cheers, Jens
-Sumit
- a0 SMC Function ID, OPTEE_SMC_CALL_WITH_REGD_ARG
- a1 Upper 32 bits of a 64-bit shared memory cookie
- a2 Lower 32 bits of a 64-bit shared memory cookie
- a3 Offset of the struct optee_msg_arg in the shared memory with the
supplied cookie
- a4-6 Not used
- a7 Hypervisor Client ID register
- Normal return register usage:
- a0 Return value, OPTEE_SMC_RETURN_*
- a1-3 Not used
@@ -154,6 +171,10 @@ struct optee_smc_call_get_os_revision_result { #define OPTEE_SMC_FUNCID_CALL_WITH_ARG OPTEE_MSG_FUNCID_CALL_WITH_ARG #define OPTEE_SMC_CALL_WITH_ARG \ OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_ARG) +#define OPTEE_SMC_CALL_WITH_RPC_ARG \
OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_RPC_ARG)+#define OPTEE_SMC_CALL_WITH_REGD_ARG \
OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG)