Re: [Xen-devel] [RFC Patch v4 2/8] ioreq: bump the number of IOREQ page to 4 pages

[Chao Gao <chao.gao@xxxxxxxxx>]

On Thu, Dec 14, 2017 at 02:50:17PM +0000, Paul Durrant wrote:
>> -----Original Message-----
>> >
>> > Hmm. That looks like it is because the ioreq server pages are not owned by
>> > the correct domain. The Xen patch series underwent some changes later in
>> > review and I did not re-test my QEMU patch after that so I wonder if
>> > mapping IOREQ pages has simply become broken. I'll investigate.
>> >
>> 
>> I have reproduced the problem locally now. Will try to figure out the bug
>> tomorrow.
>> 
>
>Chao,
>
>  Can you try my new branch 
> http://xenbits.xen.org/gitweb/?p=people/pauldu/xen.git;a=shortlog;h=refs/heads/ioreq24?
>
>  The problem was indeed that the ioreq pages were owned by the emulating 
> domain rather than the target domain, which is no longer compatible with 
> privcmd's use of HYPERVISOR_mmu_update.

Of course. I tested this branch. It works well.

But, I think your privcmd patch couldn't set 'err_ptr' to NULL when
calling xen_remap_domain_mfn_array(). It works for the ioreq page is
allocated right before the bufioreq page, and then they happen to be
continuous.

Thanks
Chao

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