linux-kernel - Re: [PATCH v2] drivers/virt: vmgenid: add vm generation id driver

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Message-ID: <CAG48ez13ZAAOVmA89PRKRqr9UezV2_bj8Q6_6sSPzcqfzbsuQQ@mail.gmail.com>
Date:   Fri, 27 Nov 2020 19:22:53 +0100
From:   Jann Horn <jannh@...gle.com>
To:     "Catangiu, Adrian Costin" <acatan@...zon.com>
Cc:     "Graf (AWS), Alexander" <graf@...zon.de>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>, Willy Tarreau <w@....eu>,
        "MacCarthaigh, Colm" <colmmacc@...zon.com>,
        Andy Lutomirski <luto@...nel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Eric Biggers <ebiggers@...nel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "bonzini@....org" <bonzini@....org>,
        "Singh, Balbir" <sblbir@...zon.com>,
        "Weiss, Radu" <raduweis@...zon.com>,
        "oridgar@...il.com" <oridgar@...il.com>,
        "ghammer@...hat.com" <ghammer@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Qemu Developers <qemu-devel@...gnu.org>,
        KVM list <kvm@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Linux API <linux-api@...r.kernel.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        linux-s390 <linux-s390@...r.kernel.org>,
        "areber@...hat.com" <areber@...hat.com>,
        Pavel Emelyanov <ovzxemul@...il.com>,
        Andrey Vagin <avagin@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
        "gil@...l.com" <gil@...l.com>,
        "asmehra@...hat.com" <asmehra@...hat.com>,
        "dgunigun@...hat.com" <dgunigun@...hat.com>,
        "vijaysun@...ibm.com" <vijaysun@...ibm.com>
Subject: Re: [PATCH v2] drivers/virt: vmgenid: add vm generation id driver

[resend in the hope that amazon will accept my mail this time instead
of replying "550 Too many invalid recipients" again]

On Fri, Nov 20, 2020 at 11:29 PM Jann Horn <jannh@...gle.com> wrote:
> On Mon, Nov 16, 2020 at 4:35 PM Catangiu, Adrian Costin
> <acatan@...zon.com> wrote:
> > This patch is a driver that exposes a monotonic incremental Virtual
> > Machine Generation u32 counter via a char-dev FS interface that
> > provides sync and async VmGen counter updates notifications. It also
> > provides VmGen counter retrieval and confirmation mechanisms.
> >
> > The hw provided UUID is not exposed to userspace, it is internally
> > used by the driver to keep accounting for the exposed VmGen counter.
> > The counter starts from zero when the driver is initialized and
> > monotonically increments every time the hw UUID changes (the VM
> > generation changes).
> >
> > On each hw UUID change, the new hypervisor-provided UUID is also fed
> > to the kernel RNG.
>
> As for v1:
>
> Is there a reasonable usecase for the "confirmation" mechanism? It
> doesn't seem very useful to me.
>
> How do you envision integrating this with libraries that have to work
> in restrictive seccomp sandboxes? If this was in the vDSO, that would
> be much easier.