linux-kernel - Re: [PATCH v2] KVM: x86/pt: Ignore all unknown Intel PT capabilities

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Message-ID: <a50909dd-fbe5-8e9c-4b98-784d3d0db178@gmail.com>
Date:   Tue, 11 Jan 2022 14:24:18 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86/pt: Ignore all unknown Intel PT capabilities

On 11/1/2022 12:20 pm, Like Xu wrote:
>> And is there any possibility of a malicious user/guest using features to cause
>> problems in the host?  I.e. does KVM need to enforce that the guest can't enable
>> any unsupported features?
> 
> If a user space is set up with features not supported by KVM, it owns the risk 
> itself.

I seem to have misunderstood it. KVM should prevent and stop any malicious guest
from destroying other parts on the host, is this the right direction ?

> 
> AFAI, the guest Intel PT introduces a great attack interface for the host and
> we only use the guest supported PT features in a highly trusted environment.
> 
> I agree that more uncertainty and fixes can be triggered in the security motive,
> not expecting too much from this patch. :D