From: Willy Tarreau <w@1wt.eu>
To: Jann Horn <jannh@google.com>
Cc: Colm MacCarthaigh <colmmacc@amazon.com>,
"Catangiu, Adrian Costin" <acatan@amazon.com>,
Andy Lutomirski <luto@kernel.org>,
Jason Donenfeld <Jason@zx2c4.com>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Eric Biggers <ebiggers@kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
"open list:VIRTIO GPU DRIVER"
<virtualization@lists.linux-foundation.org>, "Graf (AWS),
Alexander" <graf@amazon.de>,
"Woodhouse, David" <dwmw@amazon.co.uk>,
bonzini@gnu.org, "Singh, Balbir" <sblbir@amazon.com>,
"Weiss, Radu" <raduweis@amazon.com>,
oridgar@gmail.com, ghammer@redhat.com,
Jonathan Corbet <corbet@lwn.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Qemu Developers <qemu-devel@nongnu.org>,
KVM list <kvm@vger.kernel.org>, Michal Hocko <mhocko@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Pavel Machek <pavel@ucw.cz>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH] drivers/virt: vmgenid: add vm generation id driver
Date: Sat, 17 Oct 2020 09:17:21 +0200 [thread overview]
Message-ID: <20201017071721.GA14143@1wt.eu> (raw)
In-Reply-To: <CAG48ez3pXLC+eqAXDCniM0a+5yP2XJODDkZqiUTZUOttCE_LbA@mail.gmail.com>
On Sat, Oct 17, 2020 at 08:55:34AM +0200, Jann Horn wrote:
> My suggestion is to use a counter *in the UAPI*, not in the hypervisor
> protocol. (And as long as that counter can only miss increments in a
> cryptographically negligible fraction of cases, everything's fine.)
OK I got it now and I agree.
> > If what is sought is pure
> > randomness (in the sense that it's unpredictable, which I don't think
> > is needed here), then randoms are better.
>
> And this is what *the hypervisor protocol* gives us (which could be
> very useful for reseeding the kernel RNG).
As an external source, yes very likely, as long as it's not trivially
observable by everyone under the same hypervisor :-)
> > Now the initial needs in the forwarded message are not entirely clear
> > to me but I wanted to rule out the apparent mismatch between the expressed
> > needs for uniqueness and the proposed solutions solely based on randomness.
>
> Sure, from a theoretical standpoint, it would be a little bit nicer if
> the hypervisor protocol included a generation number along with the
> 128-bit random value. But AFAIU it doesn't, so if we want this to just
> work under Microsoft's existing hypervisor, we'll have to make do with
> checking whether the random value changed. :P
OK got it, thanks for the explanation!
Willy
next prev parent reply other threads:[~2020-10-17 7:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AQHWo8lIfZnFKGe8nkGmhTCXwq5R3w==>
[not found] ` <788878CE-2578-4991-A5A6-669DCABAC2F2@amazon.com>
2020-10-16 15:00 ` [PATCH] drivers/virt: vmgenid: add vm generation id driver Catangiu, Adrian Costin
2020-10-17 1:40 ` Jann Horn
2020-10-17 3:36 ` Willy Tarreau
2020-10-17 4:02 ` Jann Horn
[not found] ` <6CC3DB03-27BA-4F5E-8ADA-BE605D83A85C@amazon.com>
2020-10-17 5:01 ` Jann Horn
2020-10-17 5:29 ` Colm MacCarthaigh
2020-10-17 5:37 ` Willy Tarreau
2020-10-17 5:52 ` Jann Horn
2020-10-17 6:44 ` Willy Tarreau
2020-10-17 6:55 ` Jann Horn
2020-10-17 7:17 ` Willy Tarreau [this message]
2020-10-17 13:24 ` Jason A. Donenfeld
2020-10-17 18:06 ` Catangiu, Adrian Costin
2020-10-17 18:09 ` Alexander Graf
2020-10-18 2:08 ` Jann Horn
2020-10-20 9:35 ` Christian Borntraeger
2020-10-20 9:54 ` Alexander Graf
2020-10-20 16:54 ` Catangiu, Adrian Costin
2020-10-18 3:14 ` Colm MacCarthaigh
2020-10-18 15:52 ` Michael S. Tsirkin
2020-10-18 15:54 ` Andy Lutomirski
2020-10-18 15:59 ` Michael S. Tsirkin
2020-10-18 16:14 ` Andy Lutomirski
2020-10-19 15:00 ` Michael S. Tsirkin
2020-10-17 18:10 ` Andy Lutomirski
2020-10-19 17:15 ` Mathieu Desnoyers
2020-10-20 10:00 ` Alexander Graf
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