Xen devel - Mar 2013 - XEN-ARMv7 GIC virtualization question

Hello,

Browsing through sources of XEN-ARM for armv7 with virtualization
extensions it is not completely clear how GIC virtualization is supported.

Actually I do not understand how Dom0/DomU OS''es see GIC Distributor
registers.
In a document "ARM® Generic Interrupt Controller Architecture version 2.0
Architecture Specification" in "5.2 Managing the GIC virtual CPU
interface"
it is mentioned following:
> On the processor, the hypervisor:
>
> • configures IRQs to be taken in Hyp mode, so that it handles all IRQs
>> itself
>
> • uses the stage 2 Non-secure address translations to:
>
> — trap all Guest OS accesses to the GIC Distributor registers, so that it
>> can determine the virtual
>
> distributor settings for each virtual machine
>
> — ensure that the virtual machines cannot access the GIC virtual interface
>> control registers
>
> — remap the GIC CPU interface register address space to point to the GIC
>> virtual CPU interface registers.
>
> • configures the required maintenance interrupts from the virtual CPU
>> interface
>
>
In a function arch_domain_create() I do see mapping of GIC CPU interface
registers space of VM to point to the GIC virtual CPU interface. But
can''t
find how XEN handles VM''s accesses to GIC Distributor registers. Could
you
please explain me how is it done, or point to the correspondent code.

Sincerely,
Andrii Anisov.


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On Tue, 2013-03-05 at 19:57 +0000, Andrii Anisov wrote:
> 
> In a function arch_domain_create() I do see mapping of GIC CPU
> interface registers space of VM to point to the GIC virtual CPU
> interface. But can''t find how XEN handles VM''s accesses
to GIC
> Distributor registers. Could you please explain me how is it done, or
> point to the correspondent code. 
It''s handled from the second stage fault handler, see the call to
handle_mmio from do_trap_data_abort_guest. This eventually ends up
calling vgic_distr_mmio_handler->{read,write} AKA vgic_distr_mmio_read
(and ..._write).

Ian.