Arch Linux

brando56894

Member

From: NYC

Registered: 2008-08-03

Posts: 681

[Solved] Qemu won't create more than one core on a CPU

I'm trying to get comfortable with KVM so I switched my NAS from FreeBSD to Arch and everything works well, except for some reason now I can't get more than one CPU core to show up when I had 4 working before. I worked on this for about 8-10 hours yesterday so I don't know what I did change and what I didn't, nothing was that huge of a change. I must be specifying something incorrectly. Also the -d flag doesn't seem to work for me since there is no /tmp/qemu.log

Here's the command string that I use

sudo qemu-system-x86_64 -drive file=/Multimedia/VM-Data/arch-usenet.img,media=disk,format=raw -m 2G -cpu Broadwell -smp cpus=1,cores=4 --enable-kvm -net nic,model=virtio -net bridge,br=br0 -name arch-usenet -vga none -nographic -d guest_errors

and here's what I see on the VM itself

[root@usenet-apps ~]# cat /proc/cpuinfo 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 61
model name      : Intel Core Processor (Broadwell)
stepping        : 2
microcode       : 0x1
cpu MHz         : 2400.000
cache size      : 4096 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 ht syscall nx rdtscp lm constant_tsc rep_good nopl pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes rdrand hypervisor lahf_lm 3dnowprefetch arat smep erms
bugs            :
bogomips        : 4801.00
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

Last edited by brando56894 (2016-02-03 02:02:48)

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: [Solved] Qemu won't create more than one core on a CPU

Regarding the CPU issue, what happens if you pass -smp cores=4 or -smp cores=4,sockets=1 ?

Regarding the log, based on the docs it seems you need to specify a logfile with -D:

-d item1[,...]

    Enable logging of specified items. Use ’-d help’ for a list of log items. 
-D logfile

    Output log in logfile instead of to stderr

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But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

brando56894

Member

From: NYC

Registered: 2008-08-03

Posts: 681

Re: [Solved] Qemu won't create more than one core on a CPU

specifying --cpu Broadwell -smp cores=4 now shows 4 CPUs when I do cat /proc/cpuinfo, odd, maybe some sort of conflict? Also adding -D arch-usenet.log didn't do anything because that logfile doesn't exist anywhere.

I got that option from the qemu wiki: http://wiki.qemu.org/download/qemu-doc. … ne-options

‘-d’
Output log in /tmp/qemu.log

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: [Solved] Qemu won't create more than one core on a CPU

Unfortunately, that document is way out of date. At the very bottom:

This document was generated by Anthony Liguori on January 29, 2010

Based on that document, cpus isn't a valid option for -smp for example. It's unfortunate they keep it around, and that it's the first Google hit for "qemu command line options". The qemu wiki points out that it is "from QEMU 0.12.0 release" and recommends this instead.

Last edited by alphaniner (2016-02-02 20:03:47)

---

But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

brando56894

Member

From: NYC

Registered: 2008-08-03

Posts: 681

Re: [Solved] Qemu won't create more than one core on a CPU

Hahaha leave it to the documentation on their site to be largely out of date hahaha, it's also one of the first ones that shows up for qemu man, thanks for the heads up!

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: [Solved] Qemu won't create more than one core on a CPU

I have often referred to it by mistake when I'm on a system without qemu installed. But if qemu is installed, you should have an up-to-date copy at /usr/share/doc/qemu/qemu-doc.html

---

But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

brando56894

Member

From: NYC

Registered: 2008-08-03

Posts: 681

Re: [Solved] Qemu won't create more than one core on a CPU

Ah cool thanks, not too helpful over ssh though hahaha (everything is headless, except for my desktop. desktop -> NAS -> VMs)