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Re: RFC: PCI devices passthrough on Arm design proposal

Hi Roger,

On 20/07/2020 09:47, Roger Pau Monné wrote:
On Fri, Jul 17, 2020 at 05:18:46PM +0100, Julien Grall wrote:
Do you really need to specify the ECAM and MMIO regions there?

You need to define those values somewhere :). The layout is only shared
between the tools and the hypervisor. I think it would be better if they are
defined at the same place as the rest of the layout, so it is easier to
rework the layout.

OK, that's certainly a different approach from what x86 uses, where
the guest memory layout is not defined in the public headers.

It is mostly a convenience as some addresses are used by both the hypervisor and tools. A guest should use the firmware tables (ACPI/DT) to detect the MMIO regions.

On x86 my plan would be to add an hypercall that would set the
position of the ECAM region in the guest physmap, and that would be
called by the toolstack during domain construction.

It would be possible to use the same on Arm so the hypervisor doesn't use hardcoded values for the ECAM.


Julien Grall



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