[PATCH 0/2] vmgenid: add generation counter

[<bchalios@amazon.es>]

From: Babis Chalios <bchalios@amazon.es>

VM generation ID exposes a GUID inside the VM which changes every time a
VM restore is happening. Typically, this GUID is used by the guest
kernel to re-seed its internal PRNG. As a result, this value cannot be
exposed in guest user-space as a notification mechanism for VM restore
events.

This patch set extends vmgenid to introduce a 32 bits generation counter
whose purpose is to be used as a VM restore notification mechanism for
the guest user-space.

It is true that such a counter could be implemented entirely by the
guest kernel, but this would rely on the vmgenid ACPI notification to
trigger the counter update, which is inherently racy. Exposing this
through the monitor allows the updated value to be in-place before
resuming the vcpus, so interested user-space code can (atomically)
observe the update without relying on the ACPI notification.

Babis Chalios (2):
  vmgenid: make device data size configurable
  vmgenid: add generation counter

 docs/specs/vmgenid.txt    | 101 ++++++++++++++++++--------
 hw/acpi/vmgenid.c         | 145 +++++++++++++++++++++++++++++++-------
 include/hw/acpi/vmgenid.h |  23 ++++--
 3 files changed, 204 insertions(+), 65 deletions(-)

-- 
2.37.1

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