From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [libvirt] Setting devid for emulated NICs (Xen 4.3.1 / libvirt 1.2.0) using libxl driver Date: Thu, 19 Dec 2013 10:19:00 +0000 Message-ID: <1387448340.9925.30.camel__35281.3785001219$1387448451$gmane$org@kazak.uk.xensource.com> References: <52B07D09.5060008@canonical.com> <1387299534.1025.19.camel@dagon.hellion.org.uk> <52B08AA9.8010809@canonical.com> <1387369646.27441.129.camel@kazak.uk.xensource.com> <52B19F4E.8010601@canonical.com> <1387373284.28680.18.camel@kazak.uk.xensource.com> <52B1B842.4090306@canonical.com> <52B2415A.3030903@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52B2415A.3030903@suse.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jim Fehlig Cc: libvir-list@redhat.com, Stefan Bader , Xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Wed, 2013-12-18 at 17:44 -0700, Jim Fehlig wrote: > Stefan Bader wrote: > > On 18.12.2013 14:28, Ian Campbell wrote: > > > >> On Wed, 2013-12-18 at 14:12 +0100, Stefan Bader wrote: > >> > >>> On 18.12.2013 13:27, Ian Campbell wrote: > >>> > >>>> On Tue, 2013-12-17 at 18:32 +0100, Stefan Bader wrote: > >>>> > >>>>>> Might this libxl fix be relevant: > >>>>>> commit 5420f26507fc5c9853eb1076401a8658d72669da > >>>>>> Author: Jim Fehlig > >>>>>> Date: Fri Jan 11 12:22:26 2013 +0000 > >>>>>> > >>>>>> libxl: Set vfb and vkb devid if not done so by the caller > >>>>>> > >>>>>> Other devices set a sensible devid if the caller has not done so. > >>>>>> Do the same for vfb and vkb. While at it, factor out the common code > >>>>>> used to determine a sensible devid, so it can be used by other > >>>>>> libxl__device_*_add functions. > >>>>>> > >>>>>> Signed-off-by: Jim Fehlig > >>>>>> Acked-by: Ian Campbell > >>>>>> Committed-by: Ian Campbell > >>>>>> > >>>>>> and a follow up in dfeccbeaa. Although the comment implies that nic's > >>>>>> were already correctly assigning a devid if the caller specified -1, so > >>>>>> I don't know why it doesn't work for you :-( > >>>>>> > >>>>> Ok, yes, the commit above indeed changes libxl__device_nic_add to call > >>>>> libxl__device_nextid for the devid... Just how is this actually called. > >>>>> Maybe not sufficient but "git grep libxl__device_nic_add" in the xen code only > >>>>> shows the definition and a declaration in libxl_internal.h to me... > >>>>> > >>>> I have a feeling a macro might be involved... > >>>> > >>>> Here we go, look for DEFINE_DEVICE_REMOVE in libxl.c. We should really > >>>> add the eventual function names in comments to provide grep fodder.... > >>>> > >>> Oh duh, yeah. So in DEFINE_DEVICE_ADD a libxl_device_nic_add is created which > >>> calls to libxl__device_nic_add. When I look for the single _ version I find a > >>> call from xl_cmdimpl.c and its public declaration in libxl.h. > >>> So I guess the bug is that libvirt in the libxl driver never seems to do so > >>> > >> The macro creates libxl__add_nics which adds the nics from the > >> libxl_domain_config->nics array. I don't think libvirt needs to call > >> libxl_device_nic_add manually unless it is hotplugging a new nic at > >> runtime. > >> > >> > > > > Hm, so I think this is the path: > > > > libxl_domain_create_new > > -> do_domain_create > > -> initiate_domain_create > > -> libxl__bootloader_run (HVM domain, skipping bootloader) > > <- domcreate_bootloader_done > > -> domcreate_rebuild_done > > <- domcreate_launch_dm > > -> libxl__spawn_local_dm > > <- domcreate_devmodel_started > > > > In libxl__spawn_local_dm, there is the following loop: > > > > for (i = 0; i < d_config->num_nics; i++) { > > /* We have to init the nic here, because we still haven't > > * called libxl_device_nic_add at this point, but qemu needs > > * the nic information to be complete. > > */ > > ret = libxl__device_nic_setdefault(gc, &d_config->nics[i], domid); > > if (ret) > > goto error_out; > > } > > > > So I think when starting the dm, the devid just is not set as setdefault does > > not seem to do so. I would be done in the later domcreate_devmodel_started > > callback but that is too late for the generated qemu arguments. > > > > Sorry for jumping in late... > > I stumbled across this problem just before openSUSE13.1 released and did > a quick fix in libvirt > > https://build.opensuse.org/package/view_file/Virtualization:openSUSE13.1/libvirt/libxl-hvm-nic.patch?expand=1 > > I removed setting the NIC devid in the libxl driver a while back to be > consistent with other devices > > http://libvirt.org/git/?p=libvirt.git;a=commit;h=ba64b97134a6129a48684f22f31be92c3b6eef96 > > The quick fix was to essentially revert the above commit until I could > investigate further. Thank you for now having done that investigation > :). Can the devid assignment logic be moved from > libxl__device_nic_add() to libxl__device_nic_setdefault()? It certainly seems like it would be more natural to do it there. I suspect it might be done this way because at setdefault time you might be walking a list of nics none of which have been created yet -- so looking in xenstore would return "devid zero is free" for every one of them? How about we: * move the init to setdefault to catch the single NIC added via hotplug case * we add somewhere early in the domain create path a call to a function which assigns devids to an entire array of devices (and do it for all the different device types). Perhaps in initiate_domain_create() after the calls to libxl__domain_create_info_setdefault and libxl__domain_build_info_setdefault but before the loop calling libxl__device_disk_setdefault for the disks. * perhaps that same function should call setdefault too, after having assigned the device, rather than it being done later in an adhoc way? Does that sound at all plausible? Ian.