Re: [Xen-devel] IOREQ server on Arm

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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.

Jan



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