> -----Original Message----- > From: Jan Beulich <jbeul...@suse.com> > Sent: 18 March 2020 10:10 > To: p...@xen.org > Cc: 'David Woodhouse' <dw...@infradead.org>; sstabell...@kernel.org; > jul...@xen.org; w...@xen.org; > konrad.w...@oracle.com; george.dun...@eu.citrix.com; > andrew.coop...@citrix.com; > ian.jack...@eu.citrix.com; george.dun...@citrix.com; > jeff.kubas...@dornerworks.com; 'Xia, Hongyan' > <hongy...@amazon.com>; stewart.hildebr...@dornerworks.com; > xen-devel@lists.xenproject.org > Subject: Re: [PATCH 2/2] xen/mm: Introduce PG_state_uninitialised > > On 18.03.2020 09:53, Paul Durrant wrote: > >> -----Original Message----- > >> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of > >> David Woodhouse > >> Sent: 17 March 2020 22:15 > >> > >> On Thu, 2020-02-20 at 12:59 +0100, Jan Beulich wrote: > >>> On 07.02.2020 19:04, David Woodhouse wrote: > >>>> --- a/xen/arch/x86/mm.c > >>>> +++ b/xen/arch/x86/mm.c > >>>> @@ -488,7 +488,8 @@ void share_xen_page_with_guest(struct page_info > >>>> *page, struct domain *d, > >>>> > >>>> page_set_owner(page, d); > >>>> smp_wmb(); /* install valid domain ptr before updating refcnt. */ > >>>> - ASSERT((page->count_info & ~PGC_xen_heap) == 0); > >>>> + ASSERT((page->count_info & ~PGC_xen_heap) == PGC_state_inuse || > >>>> + (page->count_info & ~PGC_xen_heap) == > >>>> PGC_state_uninitialised); > >>> > >>> Can uninitialized pages really make it here? > >> > >> Yep, we share the low 1MiB with dom_io. > >> > > > > OOI anyone know why we do this? Is it actually necessary? > > Yes, for Dom0 to be able to access things like EBDA, IBFT, or data > found in BIOS space. >
Ok. I am still wondering why dom0's low 1MiB of pfn space is not simply mapped 1:1 though. Just historical? Paul > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
