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.) > 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. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
