Re: [PATCH v2] drivers/virt: vmgenid: add vm generation id driver

[resend in the hope that amazon will accept my mail this time instead
of replying "550 Too many invalid recipients" again]

On Fri, Nov 20, 2020 at 11:29 PM Jann Horn [off-list ref] wrote:

On Mon, Nov 16, 2020 at 4:35 PM Catangiu, Adrian Costin
[off-list ref] wrote:

quoted

This patch is a driver that exposes a monotonic incremental Virtual
Machine Generation u32 counter via a char-dev FS interface that
provides sync and async VmGen counter updates notifications. It also
provides VmGen counter retrieval and confirmation mechanisms.

The hw provided UUID is not exposed to userspace, it is internally
used by the driver to keep accounting for the exposed VmGen counter.
The counter starts from zero when the driver is initialized and
monotonically increments every time the hw UUID changes (the VM
generation changes).

On each hw UUID change, the new hypervisor-provided UUID is also fed
to the kernel RNG.

As for v1:

Is there a reasonable usecase for the "confirmation" mechanism? It
doesn't seem very useful to me.

How do you envision integrating this with libraries that have to work
in restrictive seccomp sandboxes? If this was in the vDSO, that would
be much easier.