Virtualization - Aug 2014 - [PULL] virtio-rng: add derating factor for use by hwrng core

Hi Linus,

Sending directly to you with the commit log changes Ted Ts'o pointed
out.  Not sure if Rusty's back after his travel, but this already has
his s-o-b.

Please pull.

The following changes since commit c9d26423e56ce1ab4d786f92aebecf859d419293:

  Merge tag 'pm+acpi-3.17-rc1-2' of
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm (2014-08-14
18:13:46 -0600)

are available in the git repository at:


  git://git.kernel.org/pub/scm/linux/kernel/git/amit/virtio.git rng-queue

for you to fetch changes up to 34679ec7a0c45da8161507e1f2e1f72749dfd85c:

  virtio: rng: add derating factor for use by hwrng core (2014-08-15 10:26:01
+0530)

----------------------------------------------------------------

Amit Shah (1):
  virtio: rng: add derating factor for use by hwrng core

 drivers/char/hw_random/virtio-rng.c | 1 +
 1 file changed, 1 insertion(+)

-- 
1.9.3

The khwrngd thread is started when a hwrng device of sufficient
quality is registered.  The virtio-rng device is backed by the
hypervisor, and we trust the hypervisor to provide real entropy.

A malicious or badly-implemented hypervisor is a scenario that's
irrelevant -- such a setup is bound to cause all sorts of badness, and a
compromised hwrng is the least of the user's worries.

Given this, we might as well assume that the quality of randomness we
receive is perfectly trustworthy.  Hence, we use 100% for the factor,
indicating maximum confidence in the source.

Signed-off-by: Amit Shah <amit.shah at redhat.com>
Reviewed-by: H. Peter Anvin <hpa at linux.intel.com>
Reviewed-by: Amos Kong <akong at redhat.com>
Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>

---
Pretty small and contained patch; would be great if it is picked up for
3.17.

v2: re-word commit msg (hpa)
v3: re-word commit msg (tytso)
---
 drivers/char/hw_random/virtio-rng.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/char/hw_random/virtio-rng.c
b/drivers/char/hw_random/virtio-rng.c
index 0027137..2e3139e 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -116,6 +116,7 @@ static int probe_common(struct virtio_device *vdev)
 		.cleanup = virtio_cleanup,
 		.priv = (unsigned long)vi,
 		.name = vi->name,
+		.quality = 1000,
 	};
 	vdev->priv = vi;
 
-- 
1.9.3