[PATCH v2 0/5] imx8mp: add support for the IMX AIPSTZ bridge

[Marco Felsch]

Hi Laurentiu,

On 25-02-26, Marco Felsch wrote:
> Hi,
> 
> On 25-02-26, Laurentiu Mihalcea wrote:
> > From: Laurentiu Mihalcea <laurentiu.mihalcea at nxp.com>
> > 
> > The AIPSTZ bridge offers some security-related configurations which can
> > be used to restrict master access to certain peripherals on the bridge.
> > 
> > Normally, this could be done from a secure environment such as ATF before
> > Linux boots but the configuration of AIPSTZ5 is lost each time the power
> > domain is powered off and then powered on. Because of this, it has to be
> > configured each time the power domain is turned on and before any master
> > tries to access the peripherals (e.g: AP, CM7, DSP, on i.MX8MP).
> 
> My question still stands:
> 
> Setting these bits requires very often that the core is running at EL3
> (e.g. secure-monitor) which is not the case for Linux. Can you please
> provide more information how Linux can set these bits?

Sorry I didn't noticed your response:

https://lore.kernel.org/all/a62ab860-5e0e-4ebc-af1f-6fb7ac621e2b@gmail.com/

If EL1 is allowed to set the security access configuration of the IP
cores doesn't this mean that a backdoor can be opened? E.g. your
secure-boot system configures one I2C IP core to be accessible only from
secure-world S-EL1 (OP-TEE) and after the power-domain was power-cycled
it's accessible from EL1 again. This doesn't seem right. Why should a
user be able to limit the access permissions to an IP core to only be
accessible from secure-world if the IP core is accessible from
normal-world after the power-domain was power-cycled.

Regards,
  Marco