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

From: "Jason A. Donenfeld" <Jason@zx2c4.com>
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>,
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	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>,
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	Jonathan Corbet <corbet@lwn.net>,
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	Michael Ellerman <mpe@ellerman.id.au>,
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	ghammer@redhat.com
Subject: Re: [PATCH v7 2/2] drivers/virt: vmgenid: add vm generation id driver
Date: Tue, 22 Feb 2022 22:24:19 +0100	[thread overview]
Message-ID: <CAHmME9o6cjZT1Cj1g5w5WQE83YxJNqB7eUCWn74FA9Pbb3Y6nQ@mail.gmail.com> (raw)
In-Reply-To: <1614156452-17311-3-git-send-email-acatan@amazon.com>

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