linux-kernel - Re: [PATCH v2] KVM: kvm_io_bus_unregister

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Message-Id: <20170324154051.5398a703.cornelia.huck@de.ibm.com>
Date:   Fri, 24 Mar 2017 15:40:51 +0100
From:   Cornelia Huck <cornelia.huck@...ibm.com>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        KVM list <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        stable <stable@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: kvm_io_bus_unregister_dev() should never fail

On Fri, 24 Mar 2017 07:33:01 -0300
Marcelo Tosatti <mtosatti@...hat.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.