Further I realized that I can trigger this with T3.13/Q2.5/B4.15:
trusty-lvl1-mitaka kernel: [ 931.946357] kvm [2356]: vcpu0 unhandled rdmsr:
0x140
trusty-lvl1-mitaka kernel: [ 932.236914] kvm [2356]: vcpu0 unhandled rdmsr:
0x1c9
trusty-lvl1-mitaka kernel: [ 932.238337] kvm [2356]: vcpu0 unhandled rdmsr:
0x1a6
trusty-lvl1-mitaka kernel: [ 932.239622] kvm [2356]: vcpu0 unhandled rdmsr:
0x1a7
trusty-lvl1-mitaka kernel: [ 932.240956] kvm [2356]: vcpu0 unhandled rdmsr:
0x3f6
trusty-lvl1-mitaka kernel: [ 932.242179] kvm [2356]: vcpu0 unhandled rdmsr:
0x3f7
trusty-lvl1-mitaka kernel: [ 935.038854] kvm [2356]: vcpu0 unhandled rdmsr:
0x64e
trusty-lvl1-mitaka kernel: [ 935.040086] kvm [2356]: vcpu0 unhandled rdmsr:
0x34
Which in the guest is a crash
[ 0.000000] XSAVE consistency problem, dumping leaves
[ 0.000000] WARNING: CPU: 0 PID: 0 at
/build/linux-3btXxq/linux-4.15.0/arch/x86/kernel/fpu/xstate.c:614
do_extra_xstate_size_checks+0x303/0x3e6
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.15.0-50-generic
#54-Ubuntu
[ 0.000000] RIP: 0010:do_extra_xstate_size_checks+0x303/0x3e6
[ 0.000000] RSP: 0000:ffffffffa6003d50 EFLAGS: 00010086 ORIG_RAX:
0000000000000000
[ 0.000000] RAX: 0000000000000000 RBX: 000000000000000a RCX: ffffffffa60627a8
[ 0.000000] RDX: 0000000000000001 RSI: 0000000000000086 RDI: 0000000000000047
[ 0.000000] RBP: ffffffffa6003d90 R08: 657661656c20676e R09: 0000000000000007
[ 0.000000] R10: ffffffffa625a600 R11: 0000000000000000 R12: 0000000000000100
[ 0.000000] R13: 0000000000000340 R14: ffffffffa6003d54 R15: ffffffffa6003d50
[ 0.000000] FS: 0000000000000000(0000) GS:ffffffffa627f000(0000)
knlGS:0000000000000000
[ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.000000] CR2: ffff88800008a000 CR3: 0000000013d22000 CR4: 00000000000406a0
[ 0.000000] Call Trace:
[ 0.000000] ? init_scattered_cpuid_features+0x86/0x110
[ 0.000000] fpu__init_system_xstate+0x183/0x484
[ 0.000000] fpu__init_system+0x213/0x265
[ 0.000000] ? early_init_intel+0x270/0x450
[ 0.000000] early_cpu_init+0x269/0x270
[ 0.000000] ? 0xffffffffa4c00000
[ 0.000000] setup_arch+0xcb/0xc82
[ 0.000000] ? printk+0x52/0x6e
[ 0.000000] start_kernel+0x6d/0x4fd
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x74/0x77
[ 0.000000] secondary_startup_64+0xa5/0xb0
I can avoid that particular error with a modification like:
<cpu mode='host-passthrough'>
<feature policy='disable' name='xsave'/>
</cpu>
But then another issue shows up ... (and so on)
I eventually got things running (for the tests) with
<cpu mode='host-model'>
<model fallback='forbid'/>
<feature policy='require' name='md-clear'/>
</cpu>
That might be an issue with xsave and other features in old nested, but this
further underlines my point on nested being nice but unreliable - at least "in
the past".
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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:
New
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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