> -----Original Message----- > From: Xen-devel [mailto:xen-devel-boun...@lists.xenproject.org] On Behalf > Of Olaf Hering > Sent: 27 January 2020 11:30 > To: xen-de...@lists.xen.org > Subject: Re: [Xen-devel] live migration from 4.12 to 4.13 fails due to > qemu-xen bug > > Am Mon, 13 Jan 2020 11:36:27 +0100 > schrieb Olaf Hering <o...@aepfle.de>: > > > This HVM domU fails to live migrate from staging-4.12 to staging-4.13: > > It turned out libxl does not configure qemu correctly at runtime: > libxl__build_device_model_args_new() uses 'qemu -machine xenfv', perhaps > with the assumption that 'xenfv' does the right thing. Unfortunately, > 'xenfv' entirely ignores compatibility of "pc-i440fx" between qemu > versions, 'xenfv' just maps to 'pc' aka 'the lastest'. Instead of 'qemu - > machine xenfv', libxl should run 'qemu -machine pc-i440fx-3.0 -device xen- > platform -accel xen' to make sure the domU can be migrated safely to > future versions of qemu.
Agreed, I think use xenfv needs to be dropped and xl/libxl ought to specify the pc version it wants, as you suggest. For compat though, if the pc version is not specified in xl.cfg we'd need a mechanism to scan the versions supported by the installed qemu and then pick the latest, such that it then gets baked into the json blob for save/restore/migration purposes. > > Maybe there should also be a way to select a specific variant of "pc- > i440fx". Currently the only way to do that is to use > device_model_args_hvm= in xl.cfg. Unfortunately libvirt does not support > "b_info->extra*". > Yeah, it should be a first class config option. > Should the string "pc-i440fx-3.0" become a configure option? > I suppose. Could we have "pc-i440fx" as the default, which libxl prefix matches against qemu's supported versions to select the latest? I guess that would work. Functionally your code looks fine, but I don't think fixing on 3.0 is the right thing to do. What happens if someone is trying to use an older version of qemu? It's going to cause unexpected breakage I think. Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
