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

[Andre Przywara <andre.przywara@linaro.org>]

On 04/26/2013 03:18 PM, Peter Maydell wrote:
> On 26 April 2013 14:14, Andre Przywara <andre.przywara@linaro.org> wrote:
>> 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 new U-Boot command called "hypmode"
>> which can be used at any time at the U-Boot command prompt to
>> switch the CPU into HYP mode - ideally this would be done before
>> starting the kernel.
>
> The obvious question here is "why do we need a new command?".
> The kernel booting specification says "boot the kernel in
> Hyp mode" so we should just always do that for booting Linux,
> surely?

Because it avoids regressions. I kind of feel uneasy to do a lot of 
tinkering with secure state and the GIC unconditionally, especially if 
enabled on many boards with virt-capable CPUs.

As written in question 2) later in that mail, I can also live with a 
command to _dis_able the HYP mode switching in case it causes problems.

Regards,
Andre.