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Subject: Re: [RFC PATCH 0/3] KVM: Introduce "VM bugged" concept
To:     Marc Zyngier <maz@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        Huacai Chen <chenhc@lemote.com>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        linux-mips@vger.kernel.org, Paul Mackerras <paulus@ozlabs.org>,
        kvm-ppc@vger.kernel.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>
References: <20200923224530.17735-1-sean.j.christopherson@intel.com>
 <874knlrf4a.wl-maz@kernel.org>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <100a603f-193c-5a46-d428-cfc0ce0a8fe4@redhat.com>
Date:   Fri, 25 Sep 2020 23:05:48 +0200
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On 25/09/20 18:32, Marc Zyngier wrote:
> I'm quite like the idea. However, I wonder whether preventing the
> vcpus from re-entering the guest is enough. When something goes really
> wrong, is it safe to allow the userspace process to terminate normally
> and free the associated memory? And is it still safe to allow new VMs
> to be started?

For something that bad, where e.g. you can't rule out future memory
corruptions via use-after-free bugs or similar, you're probably entering
BUG_ON territory.

Paolo