That finds us the fix as:
commit 120eee7d1fdb2eba15766cfff7b9bcdc902690b4
Author: Eduardo Habkost <[email protected]>
Date: Tue Jun 17 17:31:53 2014 -0300
target-i386: Set migratable=yes by default on "host" CPU mooel
Having only migratable flags reported by default on the "host" CPU model
is safer for the following reasons:
* Existing users may expect "-cpu host" to be migration-safe, if they
take care of always using compatible host CPUs, host kernels, and
QEMU versions.
* Users who don't care aboug migration and want to enable all features
supported by the host kernel can simply change their setup to use
migratable=no.
Without this change, people using "-cpu host" will stop being able to
migrate, because now "invtsc" is getting enabled by default.
We are not setting migratable=yes by default on all X86CPU subclasses,
because users should be able to get non-migratable features enabled if
they ask for them explicitly.
Reviewed-by: Marcelo Tosatti <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>
Signed-off-by: Andreas Färber <[email protected]>
Which is interesting, because that just is a flip in a default setting of qemu.
Maybe the interaction that qemu 2.5 and kernel 4.4 (remember it does not occur
with 3.13 kernel) comes down to a user accessible switch?
If we are running as "host-passthrough" (which we do) this change means
it does no more pass "all" flags. Instead only flags considered
"migratable" are passed to the guest.
In qemu 2.0 this differentiation didn't even exist (the infrastructure
for it was added in qemu 2.1).
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https://bugs.launchpad.net/bugs/1829555
Title:
nested virtualization w/first level trusty guests has odd MDS behavior
Status in linux package in Ubuntu:
Confirmed
Status in qemu package in Ubuntu:
Confirmed
Bug description:
When nested kvm virtualization is used (with host-passthrough), if the
first level guest is a trusty vm, odd behavior is seen in the second
level guest:
host os:
disco/5.0.0-15.16-generic/qemu 1:3.1+dfsg-2ubuntu3.1
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT vulnerable
1st level vm:
trusty/4.4.0-148.174~14.04.1-generic/qemu 2.0.0+dfsg-2ubuntu1.46
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT Host state unknown
2nd level vm:
bionic/4.15.0-50.54-generic
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Not affected
This behavior is not seen when the first level guest is a xenial or
bionic vm (same bare metal hardware):
1st level vm:
bionic/4.15.0-50.54-generic/qemu 1:2.11+dfsg-1ubuntu7.13
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT Host state unknown
2nd level vm:
bionic/4.15.0-50.54-generic
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT Host state unknown
and:
1st level vm:
xenial/4.4.0-148.174-generic/qemu 1:2.5+dfsg-5ubuntu10.39
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT Host state unknown
2nd level vm:
bionic/4.15.0-50.54-generic
contents of /sys/devices/system/cpu/vulnerabilities/mds:
Mitigation: Clear CPU buffers; SMT Host state unknown
It's not clear whether this is an issue with linux/kvm or qemu in trusty.
---
ApportVersion: 2.14.1-0ubuntu3.29
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: ubuntu 2239 F.... pulseaudio
DistroRelease: Ubuntu 14.04
HibernationDevice: RESUME=UUID=4fa9460d-7ed4-49db-8e22-86a5107d0062
InstallationDate: Installed on 2019-02-14 (92 days ago)
InstallationMedia: Ubuntu 14.04.5 LTS "Trusty Tahr" - Release amd64 (20160803)
Lsusb:
Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
Package: qemu 2.0.0+dfsg-2ubuntu1.46
PackageArchitecture: amd64
ProcEnviron:
TERM=screen
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 qxldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-148-generic
root=UUID=9a35107e-83fa-4010-81e1-235a4ea14fe6 ro quiet splash vt.handoff=7
ProcVersionSignature: User Name 4.4.0-148.174~14.04.1-generic 4.4.177
RelatedPackageVersions:
linux-restricted-modules-4.4.0-148-generic N/A
linux-backports-modules-4.4.0-148-generic N/A
linux-firmware 1.127.24
RfKill:
Tags: trusty trusty
Uname: Linux 4.4.0-148-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip libvirtd lpadmin plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: 1.12.0-1
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-bionic
dmi.modalias:
dmi:bvnSeaBIOS:bvr1.12.0-1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-bionic:cvnQEMU:ct1:cvrpc-i440fx-bionic:
dmi.product.name: Standard PC (i440FX + PIIX, 1996)
dmi.product.version: pc-i440fx-bionic
dmi.sys.vendor: QEMU
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