[U-Boot] [PATCH 0/6] ARMv7: Add HYP mode switching support

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Andre,

On Mon,  6 May 2013 15:17:44 +0200, Andre Przywara
<andre.przywara@linaro.org> wrote:

> (for GIT URL and Changelog see below)
> 
> ARM CPUs with the virtualization extension have a new mode called
> HYP mode, which allows hypervisors to safely control and monitor
> guests. The current hypervisor (KVM and Xen) implementations
> require the kernel to be entered in that HYP mode.
> 
> This patch series introduces a configuration variable
> CONFIG_ARMV7_VIRT which enables code to switch all cores into HYP
> mode. This is done automatically during execution of the bootm
> command (but could also be done earlier - U-Boot runs fine in HYP
> mode without MMU usage).
> 
> The process of switching into HYP mode requires the CPU to be in
> non-secure state, which requires the GIC to be programmed properly
> first. Explanations about the details are in the commit messages
> of the respective patches.
> 
> The code aims to be as generic as possible, though currently it has
> only been tested on the Versatile Express TC-2 board. The last patch
> thus enables the feature for that board and relies on the Versatile
> Express updates patches sent out lately[1].
> 
> For convenience there is now a GIT tree which you can pull these
> and the Versatile Express patches from ("hypmode" branch):
> git://git.linaro.org/people/aprzywara/u-boot.git
> 
> Changes from the RFC version I sent out before:
> * not a dedicated command anymore, code run by bootm & friends
> * protecting code with #ifdefs to avoid unnecessary inclusion and
>   accidental crashing (when accessing restricted registers)
> * moving prototypes to header file to meet checkpatch recommendation
> * adding comment as proposed by Christoffer
> 
> Please review and comment!
> Contributions and comments to support other boards are welcome.

I know... virtually... nothing in virtualization, so please excuse any
silly questions below:

- what happens if a target with these patches actually starts with HYP
  already enabled by some secure ROM boot code?

- I thought that once HYP is enabled, then all secure functionalities
  are performed by some monitor code invoked through a sw exception. Is
  the swi handler this monitor code? If it is, then is this monitor
  crippled, and what will happen if the bootm code needs to use some
  secure functionality?

> Andre.

Amicalement,
-- 
Albert.