Migration with Host model fails to set md-clear (not yet released in archive)

[Christian Ehrhardt ]

This s an issue found while testing for a planned update.
Filing it as bug to work together on it.

PPA: https://launchpad.net/~paelzer/+archive/ubuntu/bug-1830243-1832622-1828495-sruregressiontests/+packages

(U) = Updated to the new version
(O) = orig version as in the archive now

Migrations fails from old versions to the new Disco version:
 - Cosmic (O) -> Disco (U) -> fail
 - Disco (O) -> Disco (U) -> fail
Migration works in other cases where the same backport should be active:
 - Bionic (O) -> Bionic (U) -> works
Also it works if both peers of the migration are updated
 - Disco (U) -> Disco (U) -> works
The same worked without the update
 - Disco (O) -> Disco (O) -> works
And the same code in later versions work as well:
 - Disco (U) -> Eoan (O)

The case that fails is the recently added host-model migration check, so there might be soemthing we miss so far in the test setup.
Error:

$ virsh migrate --unsafe --live kvmguest-disco-normal qemu+ssh://10.21.151.7/system
error: internal error: process exited while connecting to monitor: 2019-07-11T21:33:29.584326Z qemu-system-x86_64: can't apply global Haswell-noTSX-IBRS-x86_64-cpu.md-clear=on: Property '.md-clear' not found

TL;DR of the case:
1. Get two Disco systems (x86)
2. one system has the base version, one the new version of qemu
3. start a guest with type "host-model"
4. migrate that guest between the two systems

[Rafael David Tinoco (rafaeldtinoco)]

AMD machine is good for host-passthrough:

(c)inaddy@kvmdisco2:~$ virsh list --all
 Id Name State
------------------------------
 3 kguest running
 - kbionic shut off
 - kdebian shut off
 - kdisco shut off
 - keoan shut off
 - kguestspice shut off
 - kxenial shut off

(c)inaddy@kvmdisco2:~$ virsh console kguest
Connected to domain kguest
Escape character is ^]

inaddy@kguest:~$

as expected! I'll reproduce this is a non-AMD machine and fix it.

[Rafael David Tinoco (rafaeldtinoco)]

Hey Christian:

Checking out my merge requests from:

https://code.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu

You can see that the upstream commit:

https://github.com/qemu/qemu/commit/4c257911dcc7

Is the same in the QEMU Bionic MR:

https://git.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu/commit/?id=da8eec6e84a0f04226d6f6e1bf5bbb80befe6c53

But something odd happened in Disco MR:

https://git.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu/commit/?id=84eb95cbd1f62d964f8986e227297a1811de234a

And the patch looks like a mix of several other patches :\, and it removed md-clear flag from FEAT_7_0_EDX (possible cause of this issue), among several other wrong things it wasn't supposed to.

I have already compared all other debian/ubuntu/patches/XX and it looks like only lp1828495-0015-remove-cpuid-intel_pt.patch was changed from one merge request to another. I'm fixing it, really unsure what happened there :\.

[Rafael David Tinoco (rafaeldtinoco)]

I have provided a fix in:

https://code.launchpad.net/~rafaeldtinoco/ubuntu/+source/qemu/+git/qemu/+merge/369470

And provided that patchset package in PPA:

https://launchpad.net/~rafaeldtinoco/+archive/ubuntu/lp1828495?field.series_filter=disco

I think we're good now, will test it in my new Intel environment (I had to create an Intel new CPU lab, migration capable, so I can workout issues with Intel CPUs).

Thanks.

[Christian Ehrhardt  (paelzer)]

Ok, I have followed what you have found and agree to the broken patch #15.
I fixed my branches and builds from your updated MP and will respin the testsuite.

Consider this bug fixed unless I reopen it.