Re: [Qemu-devel] [PATCH v2 06/23] target-arm: add arm_is_secure() function

[Peter Maydell]

On 14 May 2014 21:22, Greg Bellows <address@hidden> wrote:
> I suppose it depends on how true we want to be to the specification and
> whether our default is NS=0 or NS=1 when the security extension is present
> or not.  The code currently assumes non-secure as the default state.

The v8 ARM ARM at least allows the CPU to behave as if only
NS was present if there is no implementation of the Security
extensions. I haven't checked the v7 wording.

(In general I think QEMU's implementation of this should follow
the v8 ARM ARM and treat v7 CPUs as a sort of special degenerate
case.)

> Is there a convention in qemu?  How closely do we attempt to stay to the
> pseudo code provided in the spec?

The pseudocode in the ARM ARM is part of the spec. We should
strive to follow the spec. This doesn't necessarily mean matching
pseudocode functions exactly -- the requirement is to be
behaviourally the same, and sometimes the pseudocode is
written to be clear rather than efficient or to deal with situations
we don't necessarily care about.

thanks
-- PMM