Re: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC

[Peter Xu]

On Mon, Oct 19, 2020 at 01:05:19PM -0400, Paolo Bonzini wrote:
> Allowing userspace to intercept reads to x2APIC MSRs when APICV is
> fully enabled for the guest simply can't work.   But more in general,
> if the LAPIC is in-kernel, allowing accessed by userspace would be very
> confusing.  If userspace wants to intercept x2APIC MSRs, then it should
> first disable in-kernel APIC.
> 
> We could in principle allow userspace to intercept reads and writes to TPR,
> and writes to EOI and SELF_IPI, but while that could be made it work, it
> would still be silly.
> 
> Cc: Alexander Graf <graf@xxxxxxxxxx>
> Cc: Aaron Lewis <aaronlewis@xxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Acked-by: Peter Xu <peterx@xxxxxxxxxx>

-- 
Peter Xu