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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Tue, 22 Feb 2022 22:24:19 +0100
Message-ID: <CAHmME9o6cjZT1Cj1g5w5WQE83YxJNqB7eUCWn74FA9Pbb3Y6nQ@mail.gmail.com>
Subject: Re: [PATCH v7 2/2] drivers/virt: vmgenid: add vm generation id driver
To:     Adrian Catangiu <acatan@amazon.com>
Cc:     "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        QEMU Developers <qemu-devel@nongnu.org>,
        KVM list <kvm@vger.kernel.org>, linux-s390@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        graf@amazon.com, Randy Dunlap <rdunlap@infradead.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Mike Rapoport <rppt@kernel.org>, 0x7f454c46@gmail.com,
        borntraeger@de.ibm.com, Jann Horn <jannh@google.com>,
        Willy Tarreau <w@1wt.eu>,
        Colm MacCarthaigh <colmmacc@amazon.com>,
        Andrew Lutomirski <luto@kernel.org>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Eric Biggers <ebiggers@kernel.org>,
        "Woodhouse, David" <dwmw@amazon.co.uk>, bonzini@gnu.org,
        "Singh, Balbir" <sblbir@amazon.com>,
        "Weiss, Radu" <raduweis@amazon.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Pavel Machek <pavel@ucw.cz>,
        Michael Ellerman <mpe@ellerman.id.au>, areber@redhat.com,
        ovzxemul@gmail.com, avagin@gmail.com, ptikhomirov@virtuozzo.com,
        gil@azul.com, asmehra@redhat.com, dgunigun@redhat.com,
        vijaysun@ca.ibm.com, oridgar@gmail.com, ghammer@redhat.com
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Hi Adrian,

This thread seems to be long dead, but I couldn't figure out what
happened to the ideas in it. I'm specifically interested in this part:

On Wed, Feb 24, 2021 at 9:48 AM Adrian Catangiu <acatan@amazon.com> wrote:
> +static void vmgenid_acpi_notify(struct acpi_device *device, u32 event)
> +{
> +       uuid_t old_uuid;
> +
> +       if (!device || acpi_driver_data(device) != &vmgenid_data) {
> +               pr_err("VMGENID notify with unexpected driver private data\n");
> +               return;
> +       }
> +
> +       /* update VM Generation UUID */
> +       old_uuid = vmgenid_data.uuid;
> +       memcpy_fromio(&vmgenid_data.uuid, vmgenid_data.uuid_iomap, sizeof(uuid_t));
> +
> +       if (memcmp(&old_uuid, &vmgenid_data.uuid, sizeof(uuid_t))) {
> +               /* HW uuid updated */
> +               sysgenid_bump_generation();
> +               add_device_randomness(&vmgenid_data.uuid, sizeof(uuid_t));
> +       }
> +}

As Jann mentioned in an earlier email, we probably want this to
immediately reseed the crng, not just dump it into
add_device_randomness alone. But either way, the general idea seems
interesting to me. As far as I can tell, QEMU still supports this. Was
it not deemed to be sufficiently interesting?

Thanks,
Jason