On 4/17/24 14:09, Krzysztof Kozlowski wrote:
On 17/04/2024 12:40, Babis Chalios wrote:
Virtual Machine Generation ID driver was introduced in commit af6b54e2b5ba
("virt: vmgenid: notify RNG of VM fork and supply generation ID"), as an
ACPI only device.
VMGenID specification http://go.microsoft.com/fwlink/?LinkId=260709 defines
a mechanism for the BIOS/hypervisors to communicate to the virtual machine
that it is executed with a different configuration (e.g. snapshot execution
or creation from a template).
The guest operating system can use the notification for various purposes
such as re-initializing its random number generator etc.
As per the specs, hypervisor should provide a globally unique identified,
or GUID via ACPI.
This patch tries to mimic the mechanism to provide the same functionality
which is for a hypervisor/BIOS to notify the virtual machine when it is
executed with a different configuration.
As part of this support the devicetree bindings requires the hypervisors or
BIOS to provide a memory address which holds the GUID and an IRQ which is
used to notify when there is a change in the GUID.
The memory exposed in the DT should follow the rules defined in the
vmgenid spec mentioned above.
*Reason for this change*:
Chosing ACPI or devicetree is an intrinsic part of an hypervisor design.
Without going into details of why a hypervisor would chose DT over ACPI,
we would like to highlight that the hypervisors that have chose devicetree
and now want to make use of the vmgenid functionality cannot do so today
because vmgenid is an ACPI only device.
This forces these hypervisors to change their design which could have
undesirable impacts on their use-cases, test-scenarios etc.
The point of vmgenid is to provide a mechanism to discover a GUID when
the execution state of a virtual machine changes and the simplest
way to do it is pass a memory location and an interrupt via devicetree.
It would complicate things unnecessarily if instead of using devicetree,
we try to implement a new protocol or modify other protocols to somehow
provide the same functionility.
We believe that adding a devicetree binding for vmgenid is a simpler,
better alternative to provide the same functionality and will allow
such hypervisors as mentioned above to continue using devicetree.
More references to vmgenid specs:
- https://www.qemu.org/docs/master/specs/vmgenid.html
- https://learn.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-
machine-generation-identifier
Co-authored-by: Sudan Landge <sudanl@xxxxxxxxxx>
Signed-off-by: Babis Chalios <bchalios@xxxxxxxxx>
What happened here?
NAK
You are no the author of this patch. You changed here nothing and you
took authorship?
Read carefully submitting patches, this is not acceptable.
Hi Krzysztof,
Thanks for your review and your comments (both here and at the thread in
the previous version). I will read again the documentation for DCO on
submitting
patches.
In the meantime, I followed the suggestion of Alex in the discussion of the
previous thread and had already sent v6 before receiving yours and Jason's
responses. In my defense, I didn't want to plagiarize Sudan here. It
just seemed
from the discussion in the previous version that this is the standard
practice
when someone is taking over the submission of a patch-set.
I will re-create the patches with correct authorship, my SoB and the
Reviewed-by
tags I had received in previous versions and send a v7.
Cheers,
Babis
Best regards,
Krzysztof
