> -----Original Message----- > From: Julien Grall [mailto:julien.gr...@linaro.org] > Sent: 23 October 2017 20:04 > To: Paul Durrant <paul.durr...@citrix.com>; 'Jan Beulich' > <jbeul...@suse.com> > Cc: Julien Grall <julien.gr...@arm.com>; Andrew Cooper > <andrew.coop...@citrix.com>; George Dunlap > <george.dun...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; Roger > Pau Monne <roger....@citrix.com>; Wei Liu <wei.l...@citrix.com>; Stefano > Stabellini <sstabell...@kernel.org>; xen-de...@lists.xenproject.org; Konrad > Rzeszutek Wilk <konrad.w...@oracle.com>; Daniel De Graaf > <dgde...@tycho.nsa.gov>; Tim (Xen.org) <t...@xen.org> > Subject: Re: [Xen-devel] [PATCH v12 05/11] x86/mm: add > HYPERVISOR_memory_op to acquire guest resources > > > > On 20/10/17 11:10, Paul Durrant wrote: > >> -----Original Message----- > >> From: Julien Grall [mailto:julien.gr...@linaro.org] > >> Sent: 20 October 2017 11:00 > >> To: Paul Durrant <paul.durr...@citrix.com>; 'Jan Beulich' > >> <jbeul...@suse.com> > >> Cc: Julien Grall <julien.gr...@arm.com>; Andrew Cooper > >> <andrew.coop...@citrix.com>; George Dunlap > >> <george.dun...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; > Roger > >> Pau Monne <roger....@citrix.com>; Wei Liu <wei.l...@citrix.com>; > Stefano > >> Stabellini <sstabell...@kernel.org>; xen-de...@lists.xenproject.org; > Konrad > >> Rzeszutek Wilk <konrad.w...@oracle.com>; Daniel De Graaf > >> <dgde...@tycho.nsa.gov>; Tim (Xen.org) <t...@xen.org> > >> Subject: Re: [Xen-devel] [PATCH v12 05/11] x86/mm: add > >> HYPERVISOR_memory_op to acquire guest resources > >> > >> Hi Paul, > >> > >> On 20/10/17 09:26, Paul Durrant wrote: > >>>> -----Original Message----- > >>>> From: Jan Beulich [mailto:jbeul...@suse.com] > >>>> Sent: 20 October 2017 07:25 > >>>> To: Julien Grall <julien.gr...@linaro.org> > >>>> Cc: Julien Grall <julien.gr...@arm.com>; Andrew Cooper > >>>> <andrew.coop...@citrix.com>; George Dunlap > >>>> <george.dun...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; > Paul > >>>> Durrant <paul.durr...@citrix.com>; Roger Pau Monne > >>>> <roger....@citrix.com>; Wei Liu <wei.l...@citrix.com>; Stefano > Stabellini > >>>> <sstabell...@kernel.org>; xen-de...@lists.xenproject.org; Konrad > >> Rzeszutek > >>>> Wilk <konrad.w...@oracle.com>; Daniel De Graaf > >> <dgde...@tycho.nsa.gov>; > >>>> Tim (Xen.org) <t...@xen.org> > >>>> Subject: Re: [Xen-devel] [PATCH v12 05/11] x86/mm: add > >>>> HYPERVISOR_memory_op to acquire guest resources > >>>> > >>>>>>> On 19.10.17 at 18:21, <julien.gr...@linaro.org> wrote: > >>>>> Looking a bit more at the resource you can acquire from this hypercall. > >>>>> Some of them are allocated using alloc_xenheap_page() so not > assigned > >> to > >>>>> a domain. > >>>>> > >>>>> So I am not sure how you can expect a function > set_foreign_p2m_entry > >> to > >>>>> take reference in that case. > >>>> > >>>> Hmm, with the domain parameter added, DOMID_XEN there (for > >>>> Xen heap pages) could identify no references to be taken, if that > >>>> was really the intended behavior in that case. However, even for > >>>> Xen heap pages life time tracking ought to be done - it is for a > >>>> reason that share_xen_page_with_guest() assigns the target > >>>> domain as the owner of such pages, as that allows get_page() to > >>>> succeed for them. > >>>> > >>> > > > > Hi Julien, > > > >>> So, nothing I'm doing here is making anything worse, right? Grant tables > are > >> assigned to the guest, and IOREQ server pages are allocated with > >> alloc_domheap_page() so nothing is anonymous. > >> > >> I don't think grant tables is assigned to the guest today. They are > >> allocated using xenheap_pages() and I can't find > >> share_xen_page_with_guest(). > > > > The guest would not be able to map them if they were not assigned in > some way! > > Do you mean for PV? For HVM/PVH, we don't check whether the page is > assigned (see gnttab_map_frame).
Not there, but I though there were checks in guest_physmap_add_page() where the mfn passed back from gnttab_map_frame() is actually consumed. It's all quite convoluted though so I'm not sure. > > > See the code block at > http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/common/grant_tab > le.c;hb=HEAD#l1716 > > It calls gnttab_create_shared_page() which is what calls through to > share_xen_page_with_guest(). > > Thank you for the link, I will have a look. > > > > >> > >> Anyway, I discussed with Stefano about it. set_foreign_p2m_entry is > >> going to be left unimplemented on Arm until someone as time to > implement > >> correctly the function. > >> > > > > That makes sense. Do you still have any issues with this patch apart from > the cosmetic ones you spotted in the header? > > No. Although, may I request to add a comment in the ARM helpers about > the reference counting? > Sure. Thanks, Paul > Cheers, > > -- > Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
