Re: [Xen-devel] xen: arm: beginning the removal of mode_switch.S

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

On 08/21/2013 02:36 PM, Julien Grall wrote:
> On 08/20/2013 03:11 PM, Ian Campbell wrote:
> > So this is all pretty complex (not to mention hard to describe in ASCII)
> > and in lockstep, the secondary cpus wait twice once on the original
> > smp_cpu_up and then again on the relocated version. There is a subtle
> > reliance on the 1:1 mapping being retained in the original copy of the
> > page tables.
> Thanks for this ASCII!
>
> > I think the original wait is actually a workaround for lack of firmware
> > on the fastmodels, and should be implemented by either the firmware or
> > bootwrapper.
> BTW, this wait is an issue when the boot CPU ID is not equal to 0.
>
> I gave a quick try to move kick cpus after the HYP mode switch in
> assembly and I'm unable to boot secondary cpus on the Versatile Express.
> I guess, on the VE secondary cpus can only be "kick" in secure mode.
Right, but I think this is not specific to the VE, but ARM in general.
If I remember correctly the reason was that you cannot send IPIs from an 
non-secure GIC CPU interface to a secure one. So you have to enable the 
CPU interfaces of the others cores for non-secure operation first, which 
involves waking them up.
In my U-Boot code I switch to HYP mode on the BSP at the very end, after 
having switched the secondary cores to HYP before.
Regards,
Andre.


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