[Bug 215459] VM freezes starting with kernel 5.15

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215459

--- Comment #6 from th3voic3@mailbox.org ---
(In reply to Sean Christopherson from comment #4)
> The fix Maxim is referring to is commit fdba608f15e2 ("KVM: VMX: Wake vCPU
> when delivering posted IRQ even if vCPU == this vCPU").  But the buggy
> commit was introduced back in v5.8, so it's unlikely that's the issue, or at
> least that it's the only issue.  And assuming the VM in question has
> multiple vCPUs (which I'm pretty sure is true based on the config), that bug
> is unlikely to cause the entire VM to freeze; the expected symptom is that a
> vCPU isn't awakened when it should be, and while it's possible multiple
> vCPUs could get unlucky, taking down the entire VM is highly improbable. 
> That said, it's worth trying that fix, I'm just not very optimistic :-)
> 
> Assuming this is something different, the biggest relevant changes in v5.15
> are that the TDP MMU is enabled by default, and that the APIC access page
> memslot is not deleted when APICv is inhibited.
> 
> Can you try disabling the TDP MMU with APICv still enabled?  KVM allows that
> to be toggled without unloading, e.g. "echo N | sudo tee
> /sys/module/kvm/parameters/tdp_mmu", the VM just needs to be started after
> the param is toggled.

I enabled APICv again and toggled the setting and did a quick test. I tested a
couple of things that often caused freezes. So far so good. Now I've added the
toggle to my qemu hooks prepare section and will do further testing. 

Thanks for the input so far

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