Re: [Xen-devel] [PATCH v3 12/17] xen/arm: vpsci: Remove parameter 'ver' from do_common_cpu

[Julien Grall <julien.grall@xxxxxxx>]

On 21/02/18 16:37, Julien Grall wrote:
> On 21/02/18 16:27, Andre Przywara wrote:
> > Hi,
> Hi,
>
> > On 15/02/18 15:02, Julien Grall wrote:
> > > Currently, the behavior of do_common_cpu will slightly change depending
> > > on the PSCI version passed in parameter. Looking at the code, more the
> > > specific 0.2 behavior could move out of the function or adapted for 0.1:
> > >
> > >      - x0/r0 can be updated on PSCI 0.1 because general purpose 
> > > registers
> > >      are undefined upon CPU on.
> > Is that explicitly mentioned somewhere in the spec? I couldn't find
> > anything in the original DEN0022A. Or is that because it does *not*
> > mention anything about the GPR state that we are safe to put anything in
> > there?
> Because nothing tells you what is the GPR state when booting a secondary 
> CPUs in the ARM ARM. This is done to the specification to decide what 
> would be the value.
> Today Xen will zero them, but it is not because of specific requirements 
> just to avoid leak hypervisor content in those registers.
I have added in the commit message:
"This was deduced from the spec not mentioning the state of general 
purpose registers on CPU on."
Cheers,

--
Julien Grall

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