virtualbox.org

I'm running VirtualBox 6.1.14 on CentOS8 host and guest on a machine with 128 G RAM and 24 CPU cores. I only have one VM running and want tp assign it 4 CPUs. I tried to assgn 4 CPUs when I created the VM and I've tried both the phpVirtualBox interfave and VBoxManage modifyvm to change it. So far, I cannot get more than 1 CPU assigned.

TIA for any help.

See I have a 64bit host, but can't install 64bit guests post #1. Ignore the stuff about Hyper-V, that's for Windows PCs.

scottgus1 wrote:See I have a 64bit host, but can't install 64bit guests post #1. Ignore the stuff about Hyper-V, that's for Windows PCs.

The exact machine is a Dell PowerEdge R815 with dual AMD Opteron 6168 processors. Everything I can find says they do have AMD-v.

I have two of these machines, the other one has dual 6128 (8 core) processors and I have several Vbox VMs running on it with multiple CPUs. It is running VirtualBox 5.0.40 on CentOS 7.4.

The only thing that we could use to help is a VM's vbox.log. If AMD-V is enabled it will have a line "AMD-v with nested paging" or "AMD-v with unrestricted execution" or something like that. If the BIOS switch for AMD-v is off then the CPU's AMD-v won't get used. We can't help with how to turn it on in the BIOS.

I did find these lines:

00:00:00.172151 HM: HMR3Init: AMD-V w/ nested paging
00:00:00.465514 HM: Using AMD-V implementation 2.0
00:00:00.465520 HM: AMD-V revision = 0x1
00:00:00.465521 HM: AMD-V max ASID = 64
00:00:00.465523 HM: AMD-V features = 0x40f
00:00:00.465567 HM: VT-x/AMD-V init method: Global

I don't see anything strange in the log. Your host PC seems well-provisioned.

What happens when you try to set more than one CPU? If you get an error, please post the exact error message.

I've tried both setting the number of CPUs through the phpVirtualBox interface, and with VBoxManage modifyvm "idaho" --cpus 4

Neither give any error message, nor do they change the number of CPUs assigned.

What about doing it in the main Virtualbox window's Guest Settings? Check for any error messages there.

Just in case, note that you can only change the number of vCPUs while the VM is not running. (@scottgus1: The VBox.log file is from a VM started before this thread and still running.)

scottgus1 wrote:What about doing it in the main Virtualbox window's Guest Settings? Check for any error messages there.

This is a headless machine with no windowing system installed.

fth0 wrote:Just in case, note that you can only change the number of vCPUs while the VM is not running. (@scottgus1: The VBox.log file is from a VM started before this thread and still running.)

I have tried both, with the VM posered off and with it running (CLI only).

The log was from the VM after I had tried several things and started this thread, and have since shut it down, tried setting the number of CPUs and restarted it at least three times.

I also rebooted the host machine.

Here is the log from the most recent boot.

Can you make a guest with multiple processors on a different PC than copy the guest folder over to this host and run it? It will test if your existing host is having trouble with the multiple processors.

rpyne wrote:and with it running

This should have given you an error message: "The machine 'vm name' is already locked for a session (or being unlocked)"

scottgus1 wrote:

rpyne wrote:and with it running

This should have given you an error message: "The machine 'vm name' is already locked for a session (or being unlocked)"

No error message.