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Re: [Qemu-devel] [PATCH V3 0/2] Add option to configure guest vPMU
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From: |
Andrea Bolognani |
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Subject: |
Re: [Qemu-devel] [PATCH V3 0/2] Add option to configure guest vPMU |
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Date: |
Fri, 16 Sep 2016 14:29:16 +0200 |
On Thu, 2016-09-15 at 01:04 -0400, Wei Huang wrote:
> This patchset adds a pmu=[on/off] option to enable/disable vPMU support
> for guest VM. There are several reasons to justify this option. First,
> vPMU can be problematic for cross-migration between different SoC as perf
> counters are architecture-dependent. It is more flexible to have an option
> to turn it on/off. Secondly Secondly this option matches the "pmu" option
> as supported in libvirt. To make sure backward compatible, a PMU property
> is added to mach-virt machine types.
[...]
> Wei Huang (2):
> arm64: Add an option to turn on/off vPMU support
> arm: virt: add PMU property to mach-virt machine type
>
> hw/arm/virt-acpi-build.c | 2 +-
> hw/arm/virt.c | 15 ++++++++++++++-
> target-arm/cpu.c | 22 ++++++++++++++++++++++
> target-arm/cpu.h | 1 +
> target-arm/cpu64.c | 2 ++
> target-arm/kvm64.c | 19 +++++++++++++++----
> 6 files changed, 55 insertions(+), 6 deletions(-)
This doesn't seem to be working :(
My guest configuration looks like
<domain type='kvm'>
<name>abologna-rhel73</name>
<uuid>78f74104-65f2-4faf-9faa-26107c1071ef</uuid>
<memory unit='KiB'>2097152</memory>
<currentMemory unit='KiB'>2097152</currentMemory>
<vcpu placement='static'>4</vcpu>
<os>
<type arch='aarch64' machine='virt-2.7'>hvm</type>
<loader readonly='yes'
type='pflash'>/usr/share/AAVMF/AAVMF_CODE.fd</loader>
<nvram>/var/lib/libvirt/qemu/nvram/abologna-rhel73_VARS.fd</nvram>
<boot dev='hd'/>
</os>
<features>
<pmu state='off'/>
<gic version='2'/>
</features>
<cpu mode='host-passthrough'/>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/libexec/abologna-qemu-kvm</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/var/lib/libvirt/images/abologna-rhel73.qcow2'/>
<target dev='vda' bus='virtio'/>
<address type='virtio-mmio'/>
</disk>
<controller type='pci' index='0' model='pcie-root'/>
<controller type='virtio-serial' index='0'>
<address type='virtio-mmio'/>
</controller>
<interface type='network'>
<mac address='52:54:00:57:76:ad'/>
<source network='default'/>
<model type='virtio'/>
<address type='virtio-mmio'/>
</interface>
<serial type='pty'>
<target port='0'/>
</serial>
<console type='pty'>
<target type='serial' port='0'/>
</console>
<channel type='unix'>
<target type='virtio' name='org.qemu.guest_agent.0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
</devices>
</domain>
and based on that configuration, libvirt creates a QEMU
command line that looks like
LC_ALL=C \
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin \
QEMU_AUDIO_DRV=none \
/usr/libexec/abologna-qemu-kvm \
-name guest=abologna-rhel73,debug-threads=on \
-S \
-object
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-5-abologna-rhel73/master-key.aes
\
-machine virt-2.7,accel=kvm,usb=off \
-cpu host,pmu=off \
-drive
file=/usr/share/AAVMF/AAVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \
-drive
file=/var/lib/libvirt/qemu/nvram/abologna-rhel73_VARS.fd,if=pflash,format=raw,unit=1
\
-m 2048 \
-realtime mlock=off \
-smp 4,sockets=4,cores=1,threads=1 \
-uuid 78f74104-65f2-4faf-9faa-26107c1071ef \
-nographic \
-no-user-config \
-nodefaults \
-chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-5-abologna-rhel73/monitor.sock,server,nowait
\
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc \
-no-shutdown \
-boot strict=on \
-device virtio-serial-device,id=virtio-serial0 \
-drive
file=/var/lib/libvirt/images/abologna-rhel73.qcow2,format=qcow2,if=none,id=drive-virtio-disk0
\
-device
virtio-blk-device,scsi=off,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
\
-netdev tap,fd=25,id=hostnet0,vhost=on,vhostfd=27 \
-device virtio-net-device,netdev=hostnet0,id=net0,mac=52:54:00:57:76:ad \
-serial pty \
-chardev
socket,id=charchannel0,path=/var/lib/libvirt/qemu/channel/target/domain-5-abologna-rhel73/org.qemu.guest_agent.0,server,nowait
\
-device
virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
\
-msg timestamp=on
Inside the guest, however, even with pmu=off, I can still see
the PMU being initialized during boot
# dmesg | grep -i pmu
[ 0.000000] ACPI-PMU: Assign CPU 0 girq 23 level 0
[ 0.000000] ACPI-PMU: Assign CPU 1 girq 23 level 0
[ 0.000000] ACPI-PMU: Assign CPU 2 girq 23 level 0
[ 0.000000] ACPI-PMU: Assign CPU 3 girq 23 level 0
[ 0.087277] ACPI-PMU: Setting up 4 PMUs for CPU type 0
[ 0.576255] hw perfevents: enabled with armv8_pmuv3 PMU driver,
5 counters available
and perf can list the counters
# perf list | grep Hardware
branch-misses [Hardware event]
cache-misses [Hardware event]
cache-references [Hardware event]
cpu-cycles OR cycles [Hardware event]
instructions [Hardware event]
L1-dcache-load-misses [Hardware cache event]
L1-dcache-loads [Hardware cache event]
L1-dcache-store-misses [Hardware cache event]
L1-dcache-stores [Hardware cache event]
branch-load-misses [Hardware cache event]
branch-loads [Hardware cache event]
mem:<addr>[/len][:access] [Hardware breakpoint]
and use them
# perf stat true
Performance counter stats for 'true':
0.610960 task-clock (msec) # 0.102 CPUs utilized
0 context-switches # 0.000 K/sec
0 cpu-migrations # 0.000 K/sec
24 page-faults # 0.039 M/sec
1,383,676 cycles # 2.265 GHz
<not supported> stalled-cycles-frontend
<not supported> stalled-cycles-backend
396,335 instructions # 0.29 insns per cycle
<not supported> branches
5,536 branch-misses # 0.00% of all branches
0.006013060 seconds time elapsed
same way it can when using pmu=on or not passing any pmu=
value to QEMU.
I've tested this both on Moonshot and on ThunderX, the
behavior is the same.
Am I doing something wrong?
--
Andrea Bolognani / Red Hat / Virtualization