linux-kernel - Re: [PATCH v7 2/2] drivers/virt: vmgenid: add vm generation id driver

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Message-ID: <CAHmME9o6cjZT1Cj1g5w5WQE83YxJNqB7eUCWn74FA9Pbb3Y6nQ@mail.gmail.com>
Date:   Tue, 22 Feb 2022 22:24:19 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Adrian Catangiu <acatan@...zon.com>
Cc:     "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        QEMU Developers <qemu-devel@...gnu.org>,
        KVM list <kvm@...r.kernel.org>, linux-s390@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        graf@...zon.com, Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Mike Rapoport <rppt@...nel.org>, 0x7f454c46@...il.com,
        borntraeger@...ibm.com, Jann Horn <jannh@...gle.com>,
        Willy Tarreau <w@....eu>,
        Colm MacCarthaigh <colmmacc@...zon.com>,
        Andrew Lutomirski <luto@...nel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Eric Biggers <ebiggers@...nel.org>,
        "Woodhouse, David" <dwmw@...zon.co.uk>, bonzini@....org,
        "Singh, Balbir" <sblbir@...zon.com>,
        "Weiss, Radu" <raduweis@...zon.com>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Michael Ellerman <mpe@...erman.id.au>, areber@...hat.com,
        ovzxemul@...il.com, avagin@...il.com, ptikhomirov@...tuozzo.com,
        gil@...l.com, asmehra@...hat.com, dgunigun@...hat.com,
        vijaysun@...ibm.com, oridgar@...il.com, ghammer@...hat.com
Subject: Re: [PATCH v7 2/2] drivers/virt: vmgenid: add vm generation id driver

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@...zon.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