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Re: [Xen-devel] IOREQ server on Arm

Hi Jan,

On 09/26/2018 09:08 AM, Jan Beulich wrote:
On 26.09.18 at 00:39, <julien.grall@xxxxxxx> wrote:
Hi Paul,

I am looking at porting the IOREQ server infrastructure on Arm. I didn't
need much modification to make it run for Arm. Although, the
implementation could be simplified over the x86 implementation.

I noticed some issue while trying to implement the hypercall
XENMEM_acquire_resource. Per my understanding, all the page mapped via
that hypercall will use the type p2m_mapping_foreign.

This will result to trigger the ASSERT(fdom != dom) in get_page_from_gfn
(asm-arm/p2m.h) because the IOREQ page has been allocated to the
emulator domain and mapped to it. AFAICT x86 has the same assert in

IHMO, the ASSERT makes sense because you are only meant to map page
belonging to other domain with that type.

So I am wondering whether IOREQ server running in PVH Dom0 has been
tested? What would be the best course of action to fix the issue?

I think the p2m type needs to be chosen based on

I am thinking to introduce p2m_mapping_owned. Or do we have a p2m_type that we could re-use?


Julien Grall

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