Code review comment for ~rafaeldtinoco/ubuntu/+source/qemu:lp1828495-bionic-devel-qemu

$ sudo lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic

$ dpkg -l | grep -i qemu-kvm
ii qemu-kvm 1:2.11+dfsg-1ubuntu7.16~lp1828495~3 amd64 QEMU Full virtualization on x86 hardware

$ uname -a
Linux lockheed 4.18.0-23-generic #24~18.04.1-Ubuntu SMP Thu Jun 13 17:08:52 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

----

Alright, playing with a machine supporting CascadeLake I got:

$ sudo /usr/bin/qemu-system-x86_64 -name guest="guest" -machine accel=kvm -cpu Cascadelake-Server -m 2048 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid 7e55c71a-558f-412c-8445-db0e95fc549f -display none -no-user-config -nodefaults -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-shutdown -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -boot strict=on -kernel /var/lib/libvirt/images/guest/vmlinuz -initrd /var/lib/libvirt/images/guest/initrd.img -append "root=/dev/vda noresume console=tty0 console=ttyS0,38400n8 apparmor=0 net.ifnames=0 crashkernel=256M" -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/libvirt/images/guest/disk01.ext4.qcow2,format=qcow2,if=none,id=drive-virtio-disk0 -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x3,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 -msg timestamp=on -serial
stdio
[ 0.000000] Linux version 4.18.0-23-generic (buildd@lgw01-amd64-009) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #24~18.04.1-Ubuntu SMP Thu Jun 13 17:08:52 UTC 2019 (Ubuntu 4.18.0-23.24~18.04.1-generic 4.18.20)
[ 0.000000] Command line: root=/dev/vda noresume console=tty0 console=ttyS0,38400n8 apparmor=0 net.ifnames=0 crashkernel=256M
[ 0.000000] KERNEL supported cpus:
[ 0.000000] Intel GenuineIntel
[ 0.000000] AMD AuthenticAMD
[ 0.000000] Centaur CentaurHauls
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'

and no apparent errors. /proc/cpuinfo inside guest shows:

----
inaddy@guest:~$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 85
model name : Intel Xeon Processor (Cascadelake)
stepping : 6
microcode : 0x1
cpu MHz : 2095.076
cache size : 16384 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 arat pku ospke avx512_vnni
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds
bogomips : 4190.15
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
----

With previous QEMU I would get:

$ dpkg -l | grep -i qemu-kvm
ii qemu-kvm 1:2.11+dfsg-1ubuntu7.15 amd64 QEMU Full virtualization on x86 hardware

$ sudo /usr/bin/qemu-system-x86_64 -name guest="guest" -machine accel=kvm -cpu Cascadelake-Server -m 2048 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid 7e55c71a-558f-412c-8445-db0e95fc549f -display none -no-user-config -nodefaults -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-shutdown -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1 -boot strict=on -kernel /var/lib/libvirt/images/guest/vmlinuz -initrd /var/lib/libvirt/images/guest/initrd.img -append "root=/dev/vda noresume console=tty0 console=ttyS0,38400n8 apparmor=0 net.ifnames=0 crashkernel=256M" -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/libvirt/images/guest/disk01.ext4.qcow2,format=qcow2,if=none,id=drive-virtio-disk0 -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x3,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 -msg timestamp=on -serial stdio

2019-06-20T05:59:44.876619Z qemu-system-x86_64: unable to find CPU model 'Cascadelake-Server'

and if using regular host passthrough:

----
inaddy@guest:~$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 85
model name : Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz
stepping : 6
microcode : 0x1
cpu MHz : 2095.076
cache size : 16384 KB
physical id : 0
siblings : 1
core id : 0
cpu cores : 1
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single pti ssbd ibrs ibpb tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves arat umip pku ospke avx512_vnni md_clear
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds
bogomips : 4190.15
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:
----

I still need to test if cpuid is reporting what it is supposed to.