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    SubjectRe: [PATCH v2 0/2] STM32 Extended TrustZone Protection driver
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    On 01/03/18 14:15, Benjamin Gaignard wrote:
    > 2018-03-01 15:02 GMT+01:00 Mark Rutland <mark.rutland@arm.com>:
    >> On Thu, Mar 01, 2018 at 02:58:04PM +0100, Benjamin Gaignard wrote:
    >>> On early boot stages STM32MP1 platform is able to dedicate some hardware blocks
    >>> to a secure OS running in TrustZone.
    >>> We need to avoid using those hardware blocks on non-secure context (i.e. kernel)
    >>> because read/write accesses could generate illegale access exceptions.
    >>>
    >>> Extended TrustZone Protection driver make sure that device is disabled if
    >>> non-secure world can't acces to it.
    >>>
    >>> version 2:
    >>> - do not use notifier anymore
    >>> - change status property value in device-tree if needed
    >>> - use a list of phandle instead of hard coded array
    >>
    >> As mentioned on v1, I don't think this should be done in Linux at all.
    >>
    >> If you wish to handle this dynamically, please fixup the DT *before*
    >> entering Linux.
    >>
    >> If you want a sane default in the dts file, put status = "disabled" on
    >> all nodes which the secure world might take ownership of.
    >
    > That is the case, nodes are disabled by ealier boot stages before entering
    > in Linux but, since mistakes and/or errors are always possible, fixup the DT
    > to avoid illegal access exceptions make sense for me.

    So why not also run a test on the memory controller in case the
    bootloader made a mistake in the memory node too? As I mentioned before,
    if you can't trust the DT to describe your hardware correctly you've
    already lost.

    Robin.

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