Re: [PATCH v7 09/10] arm_ffa: efi: introduce FF-A MM communication

Abdellatif El Khlifi
2022-11-22T13:37:32Z

On Tue, Nov 15, 2022 at 11:03:51AM +0200, Ilias Apalodimas wrote:
> Hi Abdellatif
>
> On Mon, Nov 07, 2022 at 07:20:54PM +0000, Abdellatif El Khlifi wrote:
> > Add MM communication support using FF-A transport
> >
> > This feature allows accessing MM partitions services through
> > EFI MM communication protocol. MM partitions such as StandAlonneMM
> > or smm-gateway secure partitions which reside in secure world.
> >
> > An MM shared buffer and a door bell event are used to exchange
> > the data.
> >
> > The data is used by EFI services such as GetVariable()/SetVariable()
> > and copied from the communication buffer to the MM shared buffer.
> >
> > config EFI_MM_COMM_TEE
> > - bool "UEFI variables storage service via OP-TEE"
> > - depends on OPTEE
> > + bool "UEFI variables storage service via the trusted world"
> > + depends on OPTEE && ARM_FFA_TRANSPORT
>
> This shouldn't rely on both. It's either OP-TEE or FF-A

Thanks. Addressed in v8 patchset.

>
> >
> > +#if (IS_ENABLED(CONFIG_OPTEE))
>
> This separation is a bit problematic. A user can configure bot OP-TEE and
> FF-A. Those are not mutually exclusive, but for the EFI
> variables case they are. We need a better way to isolate the compilation
> choices. Why don't we make ffa_bus_discover() return -1 if FF-A isn't
> compiled in?

I agree, this is addressed in v8 patchset.

>
> > /**
> > * get_connection() - Retrieve OP-TEE session for a specific UUID.
> > *
> > @@ -143,13 +176,229 @@ static efi_status_t optee_mm_communicate(void *comm_buf, ulong dsize)
> >
> > return ret;
> > }
> > +#endif
> > +
> > +#if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT))
> > +
> > +/**
> > + * ffa_notify_mm_sp() - Announce there is data in the shared buffer
> > + *
> > + * Notifies the MM partition in the trusted world that
> > + * data is available in the shared buffer.
> > + * This is a blocking call during which trusted world has exclusive access
> > + * to the MM shared buffer.
> > + *
> > + * Return:
> > + *
> > + * 0 on success
> > + */
> > +static int ffa_notify_mm_sp(void)
> > +{
> > + struct ffa_send_direct_data msg = {0};
> > + int ret;
> > + int sp_event_ret = -1;
> > +
> > + if (!ffa_bus_ops_get())
> > + return -EINVAL;
> > +
> > + msg.data0 = FFA_SHARED_MM_BUFFER_OFFSET; /* x3 */
> > +
> > + ret = ffa_bus_ops_get()->sync_send_receive(mm_sp_id, &msg, 1);
> > + if (ret != 0)
> > + return ret;
> > +
> > + sp_event_ret = msg.data0; /* x3 */
> > +
> > + if (sp_event_ret == MM_SUCCESS)
> > + return 0;
> > +
> > + /*
> > + * Failure to notify the MM SP
> > + */
> > +
> > + return -EACCES;
> > +}
> > +
> > +/**
> > + * ffa_discover_mm_sp_id() - Query the MM partition ID
> > + *
> > + * Use the FF-A driver to get the MM partition ID.
> > + * If multiple partitions are found, use the first one.
> > + * This is a boot time function.
> > + *
> > + * Return:
> > + *
> > + * 0 on success
> > + */
> > +static int ffa_discover_mm_sp_id(void)
> > +{
> > + u32 count = 0, size = 0;
> > + int ret;
> > + struct ffa_partition_info *parts_info;
> > +
> > + if (!ffa_bus_ops_get())
> > + return -EINVAL;
> > +
> > + /*
> > + * get from the driver the count of the SPs matching the UUID
> > + */
> > + ret = ffa_bus_ops_get()->partition_info_get(mm_sp_svc_uuid, &count, NULL);
> > + if (ret != 0) {
> > + log_err("EFI: Failure in querying partitions count (error code: %d)\n", ret);
> > + return ret;
> > + }
> > +
> > + if (!count) {
> > + log_info("EFI: No MM partition found\n");
> > + return ret;
> > + }
> > +
> > + /*
> > + * pre-allocate a buffer to be filled by the driver
> > + * with ffa_partition_info structs
> > + */
> > +
> > + log_info("EFI: Pre-allocating %d partition(s) info structures\n", count);
> > +
> > + parts_info = calloc(count, sizeof(struct ffa_partition_info));
>
> I prefer sizeof(*parts_info). Same goes for all sizeof() calls.

Addressed in v8 patchset.

>
> > + if (!parts_info)
> > + return -ENOMEM;
> > +
> > + size = count * sizeof(struct ffa_partition_info);
> > +
> > + /*
> > + * ask the driver to fill the
> > + * buffer with the SPs info
> > + */
> > + ret = ffa_bus_ops_get()->partition_info_get(mm_sp_svc_uuid, &size, parts_info);
> > + if (ret != 0) {
>
> if (!ret)

Addressed in v8 patchset.

>
>
> [...]
>
> Thanks
> /Ilias