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Date: Fri, 24 Mar 2017 15:40:51 +0100
From: Cornelia Huck <cornelia.huck@de.ibm.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
        David Hildenbrand <david@redhat.com>,
        KVM list <kvm@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?UTF-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        stable <stable@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] KVM: kvm_io_bus_unregister_dev() should never fail
In-Reply-To: <20170324103257.GA5250@amt.cnet>
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        <20170323204247.GC27861@amt.cnet>
        <CACT4Y+Y9MoCVSf515_btVJn=X8kGbJNQA7ujB+XPk=UdcxKNqQ@mail.gmail.com>
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On Fri, 24 Mar 2017 07:33:01 -0300
Marcelo Tosatti <mtosatti@redhat.com> wrote:

> Still dislike the "unregister all bus devices" as that renders the guest
> unuseable. Can't you fail gracefully? Say force qemu error.

The callers are probably too varied to find a common way to do that
(multiply with different user space tools).

At least for some cases, the guest will be terminated in the near
future anyway: For example, on s390 a NULL bus will cause an error to
be propagated through KVM_RUN on the next guest->host virtio
notification, which will cause qemu to terminate the guest.

This situation is not ideal, but this is probably the most reasonable
approach.