Re: [Xen-devel] IOREQ server on Arm

[Julien Grall <julien.grall@xxxxxxx>]

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
> > p2m_get_page_from_gfn(...).
> >
> > 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
> XENMEM_rsrc_acq_caller_owned.
I am thinking to introduce p2m_mapping_owned. Or do we have a p2m_type 
that we could re-use?
Cheers,

--
Julien Grall

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