On 04/05/2016 09:32 PM, Dr. David Alan Gilbert wrote: > * Amit Shah (amit.s...@redhat.com) wrote: >> On (Tue) 23 Feb 2016 [15:02:58], Jason Wang wrote: >>>>> This means that 2.5 cannot migrate 2.4 virtual machines, right? Is that >>>>> something we want to rectify in 2.6 by making e1000-82540em an alias of >>>>> e1000 (instead of the other way round)? >>>> You're right; I misread it. With that commit (8304402033): >>>> >>>> 2.4 with e1000-82540em will not migrate to 2.5 with e1000-82540em. >>>> >>>> This is despite they're aliased (so the cmdline is backward >>>> compatible), but the migration device name actually changed. >>>> >>>> Of course, 2.5->2.4 will also not work. >>>> >>>> Since 2.4 emits 'e1000-82540em' as the device name in the migration >>>> stream, and 2.5 emits just 'e1000', we have two different names for >>>> the same device in two versions. >>>> >>>> To fix this, we'll need a hack on the dest side to allow e1000 and >>>> e1000-82540em in the migration stream for the device, and this can be >>>> done for 2.6 and 2.5.stable. >>>> >>>> Jason, can you attempt this? >>>> >>> Sure, but just need to understand the "problem". If I understand this >>> correctly, the issue only happen for JSON description at the end of >>> migration stream, and it won't break migration in fact? >> No, this does break migration. >> >> The stream contained 'e1000-82540em' as the section header for the >> device earlier. It now only has 'e1000'. So a newer qemu will only >> accept 'e1000', but not 'e1000-82540em' (from an older release). > OK, so do we need to get this fixed for 2.6 - i.e. now. > > Dave
Sorry for the late response. Have a try with 2.4 -> 2.5 migration and it works. Looking at save_section_header(), it will save se->idstr which seems always be "e1000" even if e1000-82540em is used in cli, or is there anything I missed? > >> Amit > -- > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
