Re: [Xen-devel] [ARM] SMC (and HVC) handling in hypervisor

[Julien Grall <julien.grall@xxxxxxx>]

Hi Volodymyr,

On 01/03/17 16:09, Julien Grall wrote:
> On 01/03/17 14:13, Volodymyr Babchuk wrote:
> > Hi, Julien
> Hi Volodymyr,
>
> > On 28 February 2017 at 15:51, Julien Grall <julien.grall@xxxxxxx> wrote:
> >
> > > > This e-mail is sort of follow-up to the two threads: [1] (my thread
> > > > about TEE interaction) and [2] (Edgar's thread regarding handling SMC
> > > > calls in platform_hvc). I want to discuss more broad topic there.
> > > >
> > > > Obviously, there are growing number of SMC users and current state of
> > > > SMC handling in Xen satisfies nobody. My team wants to handle SMCs in
> > > > secure way, Xilinx wants to forward some calls directly to Secure
> > > > Monitor, while allowing to handle other in userspace, etc.
> > > >
> > > > My proposition is to gather all requirements to SMC (and HVC) handling
> > > > in one place (e.g. in this mail thread). After we' will have clear
> > > > picture of what we want, we will be able to develop some solution,
> > > > that will satisfy us all. At least, I hope so :)
> > > >
> > > > Also I want to remind, that there are ARM document called "SMC Calling
> > > > Convention" [3]. According to it, any aarch64 hypervisor "must
> > > > implement the Standard Secure and Hypervisor Service calls". At this
> > > > moment XEN does not conform to this.
> > > >
> > > > So, lets get started with the requirements:
> > > > 0. There are no much difference between SMC and HVC handling (at least
> > > > according to SMCCC).
> > > > 1. Hypervisor should at least provide own UUID and version while
> > > > called by SMC/HVC
> > >
> > > Do we need to reserve the UUID for Xen?
> > Yes, I think so. But I don't know the procedure. Should be that UUID
> > registered somewhere?
> I will chat internally about it and come back to you.
Answering to myself. I should have read more carefully the spec. You 
don't need to reserve it, UUID should be uniq as long as you respect the 
algorithm to generate it (see [1]).
So someone would need to make this up when posting the patch.

Cheers,

[1] https://tools.ietf.org/html/rfc4122

--
Julien Grall

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