Re: KVM broken after suspend in most recent kernels.

From: Sean Christopherson
Date: Wed May 27 2020 - 01:13:57 EST

On Mon, May 25, 2020 at 09:15:57PM +0800, Brad Campbell wrote:
> >When you mean that KVM is broken after suspend, you mean that you can't
> >start new VMs after suspend, or do VMs that were running before suspend
> >break? I see the later on my machine. I have AMD system though, so most
> >likely this is another bug.
> >
> >Looking at the commit, I suspect that we indeed should set the IA32_FEAT_CTL
> >after resume from ram, since suspend to ram might count as a complete CPU
> >reset.
> >
> One of those "I should have clarified that" moments immediately after I
> pressed send. I've not tried suspending with a VM running. It's "can't start
> new VMs after suspend".

Don't bother testing suspending with a VM, the only thing that will be
different is that your system will hang on resume instead when running a
VM. If there are active VMs, KVM automatically re-enables VMX via VMXON
after resume, and VMXON is what's faulting.

Odds are good the firmware simply isn't initializing IA32_FEAT_CTL, ever.
The kernel handles the boot-time case, but I (obviously) didn't consider
the suspend case. I'll work on a patch.