Convincing Windows 10 it has a quadcore

So I have a rig set for pci passthrough gaming on windows 10. Intel Core i7 6700K 4.00 GHz Unlocked Quad Core Skylake and MSI Enthuastic Gaming Intel Z170A LGA 1151 DDR4 USB 3.1 ATX Motherboard. I have everything rocking and rolling via arch linux. Only issue I am running into is certain games that crash because it things windows has a dualcore or something like that. Witcher 3 needs to be throttled or it will freeze. Watchdogs 2 wont even load properly, black splash screen after launching. Other then that everything works. I was just told killing floor 2 crashes as well.

During creation, in virt-manager i give it 4 cpu's. But in further configuration, i make sure "host-passthrough" is specified. I have even tried copy host cpu configuration. Still windows "system" shows Intel Core Processor (Skylake ) 4.01 GHz (2 processors). Task manager shows Sockets: 2, Virtual processors 2, Virtual mahcine: Yes.

What am I missing? Do i need to do some cpu pinning or something?

you said you passed 4 but you actually passed 2.

4 are physical cores, the other 4 you may see are logical cores.

i7's have hyperthreading, I.E 4 phy and 4 log. They do not have 8 cores in total, but for all intensive purposes you will need to pass all '8' to the vm.

Make sure there's only one socket in the virtmanager config. Generally its better add sockets before cores/threads in the config, but some versions of Windows will only use one socket.

Should be something like 1 socket, 2 cores, 2 threads or 1,4,1 that should give you a "quad core" as far as the VM is concerned at least

You won't actually be passing through the cores on your machine instead qemu spawns separate processes for each virtualcpu

CPU pinning fixed everything. Any one else runs into this issue, take a look at the pci passthrough arch wiki under CPU Pinning. Now I understand what this actually does. No more lag on anything, however if running on SSD there isn't much... now there isn't any to the naked eye.

CPU pinning really helped out when I first started tinkering with VFIO. By any chance do you getting audio latency problems even after using setcpu?

Prior to pinning the only audio latency I had was due to a few registry issues i believe. There is a script or app you can run as admin to fix this. MSI_util its the name of the app. Might have to do some google foo to find it. Arch wiki says it doesn't work on win10 64 for the person who entered the info in that section. But its been working for me.

I was reading that some people are having success using isolcpus in kernel to correct their audio issues.

Thanks, I'll take a look into those two.