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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf
> Of Paul Durrant
> Sent: 13 December 2017 10:49
> To: 'Chao Gao' <chao.gao@xxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu
> <wei.liu2@xxxxxxxxxx>; Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Tim
> (Xen.org) <tim@xxxxxxx>; George Dunlap <George.Dunlap@xxxxxxxxxx>;
> xen-devel@xxxxxxxxxxxxx; Jan Beulich <jbeulich@xxxxxxxx>; Ian Jackson
> <Ian.Jackson@xxxxxxxxxx>
> Subject: Re: [Xen-devel] [RFC Patch v4 2/8] ioreq: bump the number of
> IOREQ page to 4 pages
> 
> > -----Original Message-----
> > From: Chao Gao [mailto:chao.gao@xxxxxxxxx]
> > Sent: 12 December 2017 23:39
> > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu
> > <wei.liu2@xxxxxxxxxx>; Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>;
> Tim
> > (Xen.org) <tim@xxxxxxx>; George Dunlap <George.Dunlap@xxxxxxxxxx>;
> > xen-devel@xxxxxxxxxxxxx; Jan Beulich <jbeulich@xxxxxxxx>; Ian Jackson
> > <Ian.Jackson@xxxxxxxxxx>
> > Subject: Re: [RFC Patch v4 2/8] ioreq: bump the number of IOREQ page to 4
> > pages
> >
> > On Tue, Dec 12, 2017 at 09:07:46AM +0000, Paul Durrant wrote:
> > >> -----Original Message-----
> > >[snip]
> > >>
> > >> Hi, Paul.
> > >>
> > >> I merged the two qemu patches, the privcmd patch [1] and did some
> > tests.
> > >> I encountered a small issue and report it to you, so you can pay more
> > >> attention to it when doing some tests. The symptom is that using the
> new
> > >> interface to map grant table in xc_dom_gnttab_seed() always fails.
> After
> > >> adding some printk in privcmd, I found it is
> > >> xen_remap_domain_gfn_array() that fails with errcode -16. Mapping
> > ioreq
> > >> server doesn't have such an issue.
> > >>
> > >> [1]
> > >>
> >
> http://xenbits.xen.org/gitweb/?p=people/pauldu/linux.git;a=commit;h=ce5
> > >> 9a05e6712
> > >>
> > >
> > >Chao,
> > >
> > >  That privcmd patch is out of date. I've just pushed a new one:
> > >
> >
> >http://xenbits.xen.org/gitweb/?p=people/pauldu/linux.git;a=commit;h=9f
> > 00199f5f12cef401c6370c94a1140de9b318fc
> > >
> > >  Give that a try. I've been using it for a few weeks now.
> >
> > Mapping ioreq server always fails, while mapping grant table succeeds.
> >
> > QEMU fails with following log:
> > xenforeignmemory: error: ioctl failed: Device or resource busy
> > qemu-system-i386: failed to map ioreq server resources: error 16
> > handle=0x5614a6df5e00
> > qemu-system-i386: xen hardware virtual machine initialisation failed
> >
> > Xen encountered the following error:
> > (XEN) [13118.909787] mm.c:1003:d0v109 pg_owner d2 l1e_owner d0, but
> > real_pg_owner d0
> > (XEN) [13118.918122] mm.c:1079:d0v109 Error getting mfn 5da5841 (pfn
> > ffffffffffffffff) from L1 entry 8000005da5841227 for l1e_owner d0,
> pg_owner
> > d2
> 
> 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.

  Paul

>   Paul
> 
> >
> > I only fixed some obvious issues with a patch to your privcmd patch:
> > --- a/arch/x86/xen/mmu.c
> > +++ b/arch/x86/xen/mmu.c
> > @@ -181,7 +181,7 @@ int xen_remap_domain_gfn_range(struct
> > vm_area_struct *vma,
> >         if (xen_feature(XENFEAT_auto_translated_physmap))
> >                 return -EOPNOTSUPP;
> >
> > -       return do_remap_gfn(vma, addr, &gfn, nr, NULL, prot, domid, pages);
> > +       return do_remap_pfn(vma, addr, &gfn, nr, NULL, prot, domid, false,
> > pages
> >  }
> >  EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_range);
> >
> > @@ -200,8 +200,8 @@ int xen_remap_domain_gfn_array(struct
> > vm_area_struct *vma,
> >          * cause of "wrong memory was mapped in".
> >          */
> >         BUG_ON(err_ptr == NULL);
> > -        do_remap_pfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> > -                    false, pages);
> > +       return do_remap_pfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> > +                       false, pages);
> >  }
> >  EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_array);
> >
> > Thanks
> > Chao
> 
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