> -----Original Message----- > From: Jan Beulich <jbeul...@suse.com> > Sent: 06 March 2020 13:52 > To: Paul Durrant <xadimg...@gmail.com> > Cc: pdurr...@amzn.com; 'Stefano Stabellini' <sstabell...@kernel.org>; 'Julien > Grall' <jul...@xen.org>; > 'Wei Liu' <w...@xen.org>; 'Konrad Rzeszutek Wilk' <konrad.w...@oracle.com>; > 'Andrew Cooper' > <andrew.coop...@citrix.com>; 'Ian Jackson' <ian.jack...@eu.citrix.com>; > 'George Dunlap' > <george.dun...@citrix.com>; 'Tim Deegan' <t...@xen.org>; 'Tamas K Lengyel' > <ta...@tklengyel.com>; xen- > de...@lists.xenproject.org; 'Roger Pau Monné' <roger....@citrix.com> > Subject: Re: [PATCH v3 5/6] mm: add 'is_special_page' macro... > > On 06.03.2020 14:48, Paul Durrant wrote: > >> -----Original Message----- > >> From: Jan Beulich <jbeul...@suse.com> > >> Sent: 06 March 2020 13:44 > >> To: Paul Durrant <xadimg...@gmail.com> > >> Cc: pdurr...@amzn.com; 'Stefano Stabellini' <sstabell...@kernel.org>; > >> 'Julien Grall' > <jul...@xen.org>; > >> 'Wei Liu' <w...@xen.org>; 'Konrad Rzeszutek Wilk' > >> <konrad.w...@oracle.com>; 'Andrew Cooper' > >> <andrew.coop...@citrix.com>; Durrant, Paul <pdurr...@amazon.co.uk>; 'Ian > >> Jackson' > >> <ian.jack...@eu.citrix.com>; 'George Dunlap' <george.dun...@citrix.com>; > >> 'Tim Deegan' > <t...@xen.org>; > >> 'Tamas K Lengyel' <ta...@tklengyel.com>; xen-devel@lists.xenproject.org; > >> 'Roger Pau Monné' > >> <roger....@citrix.com> > >> Subject: Re: [PATCH v3 5/6] mm: add 'is_special_page' macro... > >> > >> On 06.03.2020 13:35, Paul Durrant wrote: > >>>> -----Original Message----- > >>>> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of > >>>> Jan Beulich > >>>> Sent: 06 March 2020 12:20 > >>>> To: pdurr...@amzn.com > >>>> Cc: Stefano Stabellini <sstabell...@kernel.org>; Julien Grall > >>>> <jul...@xen.org>; Wei Liu > >> <w...@xen.org>; > >>>> Konrad Rzeszutek Wilk <konrad.w...@oracle.com>; Andrew Cooper > >>>> <andrew.coop...@citrix.com>; Paul > >>>> Durrant <pdurr...@amazon.com>; Ian Jackson <ian.jack...@eu.citrix.com>; > >>>> George Dunlap > >>>> <george.dun...@citrix.com>; Tim Deegan <t...@xen.org>; Tamas K Lengyel > >>>> <ta...@tklengyel.com>; xen- > >>>> de...@lists.xenproject.org; Roger Pau Monné <roger....@citrix.com> > >>>> Subject: Re: [Xen-devel] [PATCH v3 5/6] mm: add 'is_special_page' > >>>> macro... > >>>> > >>>> On 05.03.2020 13:45, pdurr...@amzn.com wrote: > >>>>> --- a/xen/arch/x86/mm/shadow/common.c > >>>>> +++ b/xen/arch/x86/mm/shadow/common.c > >>>>> @@ -2087,19 +2087,22 @@ static int sh_remove_all_mappings(struct domain > >>>>> *d, mfn_t gmfn, gfn_t > gfn) > >>>>> * The qemu helper process has an untyped mapping of this > >>>>> dom's RAM > >>>>> * and the HVM restore program takes another. > >>>>> * Also allow one typed refcount for > >>>>> - * - Xen heap pages, to match share_xen_page_with_guest(), > >>>>> - * - ioreq server pages, to match prepare_ring_for_helper(). > >>>>> + * - special pages, which are explicitly referenced and mapped > >>>>> by > >>>>> + * Xen. > >>>>> + * - ioreq server pages, which may be special pages or normal > >>>>> + * guest pages with an extra reference taken by > >>>>> + * prepare_ring_for_helper(). > >>>>> */ > >>>>> if ( !(shadow_mode_external(d) > >>>>> && (page->count_info & PGC_count_mask) <= 3 > >>>>> && ((page->u.inuse.type_info & PGT_count_mask) > >>>>> - == (is_xen_heap_page(page) || > >>>>> + == (is_special_page(page) || > >>>>> (is_hvm_domain(d) && is_ioreq_server_page(d, > >>>>> page))))) ) > >>>> > >>>> Shouldn't you delete most of this line, after the previous patch > >>>> converted the ioreq server pages to PGC_extra ones? > >>> > >>> I thought that too originally but then I realise we still have to > >>> cater for the 'legacy' emulators that still require IOREQ server > >>> pages to be mapped through the p2m, in which case they will not > >>> be PGC_extra pages. > >> > >> Oh, indeed. (I don't suppose we can ever do away with this legacy > >> mechanism?) > > > > It's tricky because it would either mean breaking older (pre > > resource-mapping) QEMUs, > > Didn't even qemu-trad get switched? (Anyway, not a big deal here, > just would have been nice if this large conditional could have > been shrunk a little in size.)
Yes, trad is switched but I thought our position was that we supported use of arbitrary distro versions of QEMU in which case any compat code really does have to stick around for a very long time :-( > > > or allowing the toolstack to allocate the 'special' pages with > > an extra flag to make them PGC_extra. > > Doesn't sound impossible, but also not something we want to eagerly > go for. > No, probably not worth it just to save doing this test. Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
