> -----Original Message----- > From: David Woodhouse <dw...@infradead.org> > Sent: 06 March 2020 11:53 > To: Jan Beulich <jbeul...@suse.com>; Durrant, Paul <pdurr...@amazon.co.uk> > Cc: jul...@xen.org; andrew.coop...@citrix.com; sstabell...@kernel.org; > konrad.w...@oracle.com; > volodymyr_babc...@epam.com; ian.jack...@eu.citrix.com; w...@xen.org; > george.dun...@citrix.com; xen- > de...@lists.xenproject.org > Subject: RE: [EXTERNAL][PATCH 2/2] domain: use PGC_extra domheap page for > shared_info > > On Fri, 2020-03-06 at 12:37 +0100, Jan Beulich wrote: > > I've started looking at the latest version of Paul's series, but I'm > > still struggling to see the picture: There's no true distinction > > between Xen heap and domain heap on x86-64 (except on very large > > systems). Therefore it is unclear to me what "those pages" is actually > > referring to above. Surely new Xen can't be given any pages in use > > _in any way_ by old Xen, no matter whether it's ones assigned to > > domains, or ones used internally to (old) Xen. > > Old and new Xen do not coexist. There is a kexec (via kexec_reloc.S and > purgatory) from old to new. > > There are some pages which new Xen MUST NOT scribble on, because they > actually belong to the domains being preserved. That includes the EPT > (or at least IOMMU) page tables. > > I suppose new Xen also mustn't scribble on the pages in which old Xen > has placed the migration information for those domains either. At > least, not until it's consumed the data. > > Anything else, however, is fine for new Xen to scribble on. Fairly much > anything that the old Xen had allocated from its xenheap (and not > subsequently shared to a guest, qv) is no longer required and can be > treated as free memory by the new Xen, which now owns the machine. >
... so getting rid of shared xenheap pages altogether just makes life easier. Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
