linux-kernel - Re: [PATCH v4] virt: vmgenid: introduce driver for reinitializing RNG on VM fork

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Date:   Fri, 25 Feb 2022 15:33:44 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Alexander Graf <graf@...zon.com>
Cc:     kvm@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        adrian@...ity.io, ardb@...nel.org, ben@...portsystems.com,
        berrange@...hat.com, colmmacc@...zon.com, decui@...rosoft.com,
        dwmw@...zon.co.uk, ebiggers@...nel.org, ehabkost@...hat.com,
        gregkh@...uxfoundation.org, haiyangz@...rosoft.com,
        imammedo@...hat.com, jannh@...gle.com, kys@...rosoft.com,
        lersek@...hat.com, linux@...inikbrodowski.net, mst@...hat.com,
        qemu-devel@...gnu.org, raduweis@...zon.com, sthemmin@...rosoft.com,
        tytso@....edu, wei.liu@...nel.org
Subject: Re: [PATCH v4] virt: vmgenid: introduce driver for reinitializing
 RNG on VM fork

On Fri, Feb 25, 2022 at 03:18:43PM +0100, Alexander Graf wrote:
> > I recall this part of the old thread. From what I understood, using
> > "VMGENID" + "QEMUVGID" worked /well enough/, even if that wasn't
> > technically in-spec. Ard noted that relying on _CID like that is
> > technically an ACPI spec notification. So we're between one spec and
> > another, basically, and doing "VMGENID" + "QEMUVGID" requires fewer
> > changes, as mentioned, appears to work fine in my testing.
> >
> > However, with that said, I think supporting this via "VM_Gen_Counter"
> > would be a better eventual thing to do, but will require acks and
> > changes from the ACPI maintainers. Do you think you could prepare your
> > patch proposal above as something on-top of my tree [1]? And if you can
> > convince the ACPI maintainers that that's okay, then I'll happily take
> > the patch.
> 
> 
> Sure, let me send the ACPI patch stand alone. No need to include the 
> VMGenID change in there.

That's fine. If the ACPI people take it for 5.18, then we can count on
it being there and adjust the vmgenid driver accordingly also for 5.18.

I just booted up a Windows VM, and it looks like Hyper-V uses
"Hyper_V_Gen_Counter_V1", which is also quite long, so we can't really
HID match on that either.

Jason