[Xen-devel] arm: How DomU access to iomem is implemented

[Andrii Anisov <andrii.anisov@xxxxxxxxxxxxxxx>]

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.

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.

Sincerely,

Andrii Anisov.

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