Re: [Qemu-devel] [PATCH v3 0/3] rng-builtin: add an RNG backend that uses qemu_guest_getrandom()

[Markus Armbruster]

Kashyap Chamarthy <address@hidden> writes:

> On Mon, May 13, 2019 at 08:36:23AM +0200, Laurent Vivier wrote:
>> On 12/05/2019 20:21, Michael S. Tsirkin wrote:
>
> [...]
>
>> > > Kashyap Chamarthy (1):
>> > >    VirtIO-RNG: Update default entropy source to `/dev/urandom`
>> > > 
>> > > Laurent Vivier (2):
>> > >    rng-builtin: add an RNG backend that uses qemu_guest_getrandom()
>> > >    virtio-rng: change default backend to rng-builtin
>> > 
>> > 
>> > OK pls address Marku's comment on commit msg and I will merge.
>> 
>> Kashyap,
>> 
>> as this patch is from you, do you agree?
>
> Yes.
>
>> If so, I can update the message and send a new version of the series
>> (or you canr esend your patch alone if you prefer).
>
> Please go ahead and add it, the below is the text (from Dan/Markus):
>
>     What about other OSes?
>     ----------------------
>     
>     `/dev/urandom` exists and works on OS-X, FreeBSD, DragonFlyBSD, NetBSD
>     and OpenBSD, which cover all the non-Linux platforms we explicitly
>     support, aside from Windows.
>     
>     On Windows `/dev/random` doesn't work either so we don't regress.
>     This is actually another argument in favour of using the newly
>     proposed 'rng-builtin' backend by default, as that will work on
>     Windows.

Additionally, please insert "on Linux" into the first paragraph, like
this:

  When QEMU exposes a VirtIO-RNG device to the guest, that device needs a
  source of entropy, and that source needs to be "non-blocking", like
  `/dev/urandom`.  However, currently QEMU defaults to the problematic
  `/dev/random`, which on Linux is "blocking" (as in, it waits until
  sufficient entropy is available).