Re: arm: How DomU access to iomem is implemented

[Julien Grall <julien.grall@linaro.org>]

On 06/08/2013 01:49 PM, Andrii Anisov wrote:

> Hello,

Hello,

> Could you please clarify how DomU gets an access to iomem (for ARMv7VE)?

> We traced that iomem configuration of the DomU comes to hypervisor with
> /XEN_DOMCTL_iomem_permission/ domctl. Here iomem space is added to
> domain's /iomem_caps/ ranges. But we did not found how these ranges are
> actually mapped for DomU. Really these configuration looks unused, on
> our board DomU is killed by hypervisor once it tries to access f.e. real
> UART.


You need to use XEN_DOMCTL_memory_mapping. It will give access and map
region in the guest.
This hypercall is still missing on ARM, so you need to implement it.

> Actually we did a workaround by mapping regions using
> /map_mmio_regions() /right here in /XEN_DOMCTL_iomem_permission/
> handling. But it's a real hack, and it would good to know proper way to
> get stuff working.


Your solution with map_mmio_regions looks good for me.

Cheers,

-- 
Julien