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[v3,1/1] virtio: rng: add derating factor for use by hwrng core

Message ID d05dff370dcac5aa2ce4e41a3936543253565d89.1408078439.git.amit.shah@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Amit Shah Aug. 15, 2014, 5:16 a.m. UTC 
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@redhat.com>
Reviewed-by: H. Peter Anvin <hpa@linux.intel.com>
Reviewed-by: Amos Kong <akong@redhat.com>
Signed-off-by: Rusty Russell <rusty@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(+)
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Patch

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;