On Mon, 2014-11-24 at 12:06 +0000, M A Young wrote: > > On Mon, 24 Nov 2014, George Dunlap wrote: > > > On Mon, Nov 24, 2014 at 12:07 AM, M A Young <m.a.yo...@durham.ac.uk> wrote: > >> On Sat, 22 Nov 2014, M A Young wrote: > >> > >>> While investigating a bug reported on Red Hat Bugzilla > >>> https://bugzilla.redhat.com/show_bug.cgi?id=1166461 > >>> I discovered the following > >>> > >>> xl migrate --debug domid localhost does indeed fail for Xen 4.4 pv (the > >>> bug report is for Xen 4.3 hvm ) when xl migrate domid localhost works. > >>> There > >>> are actually two issues here > >>> > >>> * the segfault in libxl-save-helper --restore-domain (as reported in the > >>> bug above) occurs if the guest memory is 1024M (on my 4G box) and is > >>> presumably because the allocated memory eventually runs out > >> > >> > >> I have found a bit more out about this. The segfault at at line 1378 of > >> tools/libxc/xc_domain_restore.c which is > >> DPRINTF("************** pfn=%lx type=%lx gotcs=%08lx " > >> "actualcs=%08lx\n", pfn, pagebuf->pfn_types[pfn], > >> csum_page(region_base + (i + curbatch)*PAGE_SIZE), > >> csum_page(buf)); > >> and is because pfn in pagebuf->pfn_types[pfn] is beyond the end of the > >> array. This occurs in the verification phase. > >> > >>> * the segfault doesn't occur if the guest memory is 128M, but the > >>> migration still fails. The first attached file contains the log from a run > >>> with xl -v migrate --debug domid localhost (with mfn and duplicated lines > >>> stripped out to make the size manageable). > >> > >> > >> The difference actually seems to be down to how active the VM is rather > >> than > >> the memory size (my small memory test system was doing very little, my > >> larger system was a full OS install). In the non-segfault case the problem > >> was the printf and printf_info commands in the create_domain() routine in > >> tools/libxl/xl_cmdimpl.c . As xl migrate uses stdout to pass status > >> messages > >> back from the restoring dom0, these commands cause an unexpected message. > >> If > >> you move them onto stderr then the migration completes in the non-segfault > >> case. > > > > Good job tracking those down -- are there patches in the works? > > I have a partial patch for the printf printf_info problem, which works for > me but doesn't cover printing the info in sxp format.
Am I right that is all related to the use of --debug and or -vm? and that a plain "xl migrate" works ok? It's still a bug of course, but changes the severity (somehow, not sure to what extent IMHO it does etc). > I haven't worked out > what is leading up to the segfault yet. > > Michael Young _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
