Hi Ilias,
Please see my response inline marked [SAMI].
Regards,
Sami Mujawar
-----Original Message-----
From: Ilias Apalodimas <ilias.apalodi...@linaro.org>
Sent: 01 February 2021 02:01 PM
To: Sami Mujawar <sami.muja...@arm.com>
Cc: Sughosh Ganu <sughosh.g...@linaro.org>; devel@edk2.groups.io; Ard
Biesheuvel <ard.biesheu...@arm.com>; Leif Lindholm <l...@nuviainc.com>; Sahil
Malhotra <sahil.malho...@linaro.org>
Subject: Re: [PATCH edk2-platforms v3 1/2] Drivers/OpTeeRpmb: Add an OP-TEE
backed RPMB driver
Hi Sami,
[...]
> > +STATIC
> > +EFI_STATUS
> > +ReadWriteRpmb (
> > + UINTN SvcAct,
> > + UINTN Addr,
> > + UINTN NumBytes,
> > + UINTN Offset
> > + )
> > +{
> > + ARM_SVC_ARGS SvcArgs;
> > + EFI_STATUS Status;
> > +
> > + ZeroMem (&SvcArgs, sizeof (SvcArgs));
> > +
> > + SvcArgs.Arg0 = ARM_SVC_ID_FFA_MSG_SEND_DIRECT_REQ_AARCH64;
> > + SvcArgs.Arg1 = storage_id;
> > + SvcArgs.Arg2 = 0;
> > + SvcArgs.Arg3 = SvcAct;
> > + SvcArgs.Arg4 = Addr;
> > + SvcArgs.Arg5 = NumBytes;
> > + SvcArgs.Arg6 = Offset;
> > +
> > + ArmCallSvc (&SvcArgs);
> > + if (SvcArgs.Arg3) {
> > + DEBUG ((DEBUG_ERROR, "%a: Svc Call 0x%08x Addr: 0x%08x len: 0x%x
> > Offset: 0x%x failed with 0x%x\n",
> > + __func__, SvcAct, Addr, NumBytes, Offset, SvcArgs.Arg3));
> > + }
> > +
> > + switch (SvcArgs.Arg3) {
> > + case ARM_SVC_SPM_RET_SUCCESS:
> > + Status = EFI_SUCCESS;
> > + break;
> > +
> > + case ARM_SVC_SPM_RET_NOT_SUPPORTED:
> > + Status = EFI_UNSUPPORTED;
> > + break;
> > +
> > + case ARM_SVC_SPM_RET_INVALID_PARAMS:
> > + Status = EFI_INVALID_PARAMETER;
> > + break;
> > +
> > + case ARM_SVC_SPM_RET_DENIED:
> > + Status = EFI_ACCESS_DENIED;
> > + break;
> > +
> > + case ARM_SVC_SPM_RET_NO_MEMORY:
> > + Status = EFI_BAD_BUFFER_SIZE;
> > + break;
> > +
> > + default:
> > + Status = EFI_ACCESS_DENIED;
> > + }
> > [SAMI] Should the error handling here be updated similar to the FF-A
> > StandaloneMmPkg patches?
> > [/SAMI]
>
> I actually picked up the error handling from the previous non-FFA code.
> I'll check what's on Sughosh latest patches and fix it if there are
> any differences.
> Looking at it again EFI_BAD_BUFFER_SIZE can change to indicate out of
> memory properly anyway.
>
Had another look at this. This seems fine if I just change
EFI_BAD_BUFFER_SIZE -> EFI OUT_OF_RESOURCES because OP-TEE is only
using these errors from FFA. Eventually the OP-TEE code that launches
StMM today, will move to FFA and become a separate SP, so that will
naturally be handled once that's done. I don't see a point of adding
unused error cases.
[SAMI] Referring to the FFA specification, DEN0077A, v1.0, section 10.2
FFA_MSG_SEND_DIRECT_REQ and Table 10.8: FFA_ERROR encoding, I think the
error codes being handled above would be returned in SvcArgs.Arg2.
The message flow would be as follows:
- Caller sends FFA_MSG_SEND_DIRECT_REQ to the target endpoint.
- if the message does not reach the target endpoint, an error code from
Table 10.8 may be returned in w2 (i.e. SvcArgs.Arg2)
- If the message reaches the target endpoint, then callee shall invoke one
of the following interfaces:
* FFA_MSG_SEND_DIRECT_RESP
* FFA_INTERRUPT
* FFA_SUCCESS
This would mean that if the callee responds with FFA_MSG_SEND_DIRECT_RESP,
the callee returned error/status code shall be in w/x3-w/x7 (which I think in
this case may be in SvcArgs.Arg3).
[/SAMI]
Regards
/Ilias
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