Hi,
On 09/26/2018 10:14 AM, Paul Durrant wrote:
-----Original Message-----
From: Jan Beulich [mailto:jbeul...@suse.com]
Sent: 26 September 2018 09:09
To: Julien Grall <julien.gr...@arm.com>; Paul Durrant
<paul.durr...@citrix.com>
Cc: Andrew Cooper <andrew.coop...@citrix.com>; Roger Pau Monne
<roger....@citrix.com>; Stefano Stabellini <sstabell...@kernel.org>; xen-
devel <xen-devel@lists.xenproject.org>
Subject: Re: IOREQ server on Arm
On 26.09.18 at 00:39, <julien.gr...@arm.com> 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.
Yes, that's correct. There is a FIXME clause in acquire_resource so that that
only caller owned resources can be mapped by HVM/PVH domains. Thus the new call
can be used for IOREQ server pages, but not grant frames.
I don't understand your last sentence. IOREQ is caller owned and
therefore should work.
As I said, I don't have any problem with mapping the resource. The
problem is when unmapping it because the region is set with
p2m_mapping_foreign. You will reach the ASSERT(fdom != p2m->domain) in
p2m_get_page_from_gfn.
Regardless the reference problem (we support it on Arm). Can you explain
how this is working on PVH Dom0 today?
Cheers,
--
Julien Grall
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