devel/migration/compatibility.rst

23 Related to this are the "latest" machine types defined on each of
34 device feature exposure.  But that is not relevant for this section.
42   This is the latest QEMU with the latest machine type.
43   This have to work, and if it doesn't work it is a bug.
50 This are the easiest ones, we will not talk more about them in this
56 QEMU version, in this case pc-5.1.
61   were configured on 5.1, but this should be easy in the sense that
67   This combination is not possible as the qemu-5.1 doesn't understand
77   This migration is known as newer to older.  We need to make sure
85   This migration is known as older to newer.  We need to make sure
128 In qemu-5.2 virtio-blk-device got multi queue support.  This is a
143 So, how can we address this problem.  Easy, just convince qemu-5.2
163 And now the other interesting case, case 3.  In this case we have:
173     Think what happens if we do one of this double migrations:
190 Now, how was this done in reality?  The following commit shows how it
229 How can we get this to work with migration.  The way to do that is
236 Notice that this is not completely related to QEMU.  The most
237 important thing here is that this should be handled by the managing
266 Doing this would be the equivalent of doing with cpus:
276 When both hosts have different cpu features this is guaranteed to
302 configuration is correct.  QEMU doesn't know how to look at this kind
306 used in this example because it makes the example simpler.
312 In this section we have considered that we are using the same QEMU
332   This migration works
336   This migration works
340   This migration fails
344   This migration fails
348 pointed to this commit.
350 In qemu-8.0 we got this commit::
359 The relevant bits of the commit for our example are this ones::
379 The following commit shows how this got fixed::
408 Now we see how the fix is done.  This is going to depend on what kind
409 of breakage happens, but in this case it is quite simple::
453 And now, when qemu-8.0.1 is released with this fix, all combinations
478 This two are the ones that work. The whole point of making the
479 change in qemu-8.0.1 release was to fix this issue:
495 Yeap.  If we know that we are going to do this migration:
507 this example:
513 continue having this mark/property until we have this machine