linux-kernel - [PATCH 0/2] virt: vmgenid: add generation counter

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Message-ID: <20220803152127.48281-1-bchalios@amazon.es>
Date:   Wed, 3 Aug 2022 17:21:25 +0200
From:   <bchalios@...zon.es>
To:     <linux-kernel@...r.kernel.org>
CC:     <bchalios@...zon.es>, <tytso@....edu>, <Jason@...c4.com>,
        <dwmw@...zon.co.uk>, <graf@...zon.de>, <xmarcalx@...zon.co.uk>,
        <gregkh@...uxfoundation.org>
Subject: [PATCH 0/2] virt: vmgenid: add generation counter

From: Babis Chalios <bchalios@...zon.es>

Linux recently added support for the VM Generation ID mechanism from
Microsoft. The way this works currently is using the 128-bit blob
provided by the vmgenid device to re-seed the RNG. While this works it
has two main issues, (a) it is inherently racy due to the fact that it
relies on a ACPI notification being delivered and handled and (b) the ID
is unsuitable for exposing to user-space.

This patch-set extends the vmgenid device to introduce a generation
counter, a 32-bit counter which is different every time the unique ID
changes. The addition to the original implementation in QEMU can be
found here:
https://lists.nongnu.org/archive/html/qemu-devel/2022-08/msg00524.html.

The first patch re-works slightly the current vmgenid driver to add a
function that parses an object from the vmgenid device and returns the
physical address of the vmgenid data. The second patch uses that
function to parse additionally the address of the generation counter
from the vmgenid namespace. The counter is then exposed to the
user-space through a misc-device which provides `read` and `mmap`
interfaces.

Babis Chalios (2):
  virt: vmgenid: add helper function to parse ADDR
  virt: vmgenid: add support for generation counter

 Documentation/virt/vmgenid.rst | 120 ++++++++++++++++++++++++++
 drivers/virt/vmgenid.c         | 151 ++++++++++++++++++++++++++++-----
 2 files changed, 251 insertions(+), 20 deletions(-)
 create mode 100644 Documentation/virt/vmgenid.rst

-- 
2.37.1

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