>>> On 03.01.18 at 17:06, <paul.durr...@citrix.com> wrote: >> -----Original Message----- >> From: Jan Beulich [mailto:jbeul...@suse.com] >> Sent: 03 January 2018 15:48 >> To: Paul Durrant <paul.durr...@citrix.com> >> Cc: JulienGrall <julien.gr...@arm.com>; Andrew Cooper >> <andrew.coop...@citrix.com>; Wei Liu <wei.l...@citrix.com>; George >> Dunlap <george.dun...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; >> Stefano Stabellini <sstabell...@kernel.org>; xen-devel@lists.xenproject.org; >> Konrad Rzeszutek Wilk <konrad.w...@oracle.com>; Tim (Xen.org) >> <t...@xen.org> >> Subject: Re: [PATCH v17 06/11] x86/hvm/ioreq: add a new mappable >> resource type... >> >> >>> On 03.01.18 at 13:19, <paul.durr...@citrix.com> wrote: >> > +static void hvm_free_ioreq_mfn(struct hvm_ioreq_server *s, bool buf) >> > +{ >> > + struct domain *d = s->domain; >> > + struct hvm_ioreq_page *iorp = buf ? &s->bufioreq : &s->ioreq; >> > + >> > + if ( !iorp->page ) >> > + return; >> > + >> > + page_list_add_tail(iorp->page, &d- >> >arch.hvm_domain.ioreq_server.pages); >> >> Afaict s->domain is the guest, not the domain containing the >> emulator. Hence this new model of freeing the pages is safe only >> when the emulator domain is dead by the time the guest is being >> cleaned up. > > From the investigations done w.r.t. the grant table pages I don't think this > is the case. The emulating domain will have references on the pages and this > keeps the target domain in existence, only completing domain destruction when > the references are finally dropped. I've tested this by leaving an emulator > running whilst I 'xl destroy' the domain; the domain remains as a zombie > until emulator terminates.
Oh, right, I forgot about that aspect. >> What is additionally confusing me is the page ownership: Wasn't >> the (original) intention to make the pages owned by the emulator >> domain rather than the guest? I seem to recall you referring to >> restrictions in do_mmu_update(), but a domain should always be >> able to map pages it owns, shouldn't it? > > I'm sure we had this discussion before. I am trying to make resource mapping > as uniform as possible so, like the grant table pages, the ioreq server pages > are assigned to the target domain. Otherwise the domain trying to map > resources has know which actual domain they are assigned to, rather than the > domain they relate to... which is pretty ugly. Didn't I suggest a slight change to the interface to actually make this not as ugly? >> Furthermore you continue to use Xen heap pages rather than >> domain heap ones. > > Yes, this seems reasonable since Xen will always need mappings of the pages > and the aforementioned reference counting only works for Xen heap pages AIUI. share_xen_page_with_guest() makes any page a Xen heap one. See vmx_alloc_vlapic_mapping() for an example. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
