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

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Message-ID: <20201019173547.GB3203@xz-x1>
Date:   Mon, 19 Oct 2020 13:35:47 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Alexander Graf <graf@...zon.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC

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@...zon.com>
> Cc: Aaron Lewis <aaronlewis@...gle.com>
> Cc: Peter Xu <peterx@...hat.com>
> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Acked-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu