On Mon, Jul 21, 2014 at 2:29 PM, Antti Kantee <[email protected]> wrote:
> One more thing to take into consideration in revamping the hypercall is
> that not necessary all platforms can deliver random numbers to guests
> (e.g. Xen), except by collecting some random events and mixing and
> mashing.  For those platforms, we should just signal that getrandom()
> never returns anything, and use the in-rump-kernel rnd_add_foo() to seed
> the pool.  That way we don't need to implement the tricky entropy
> collection in the hypercall layer.

Agreed, it should return an error code rather than always returning no bytes.

I don't really know why Xen does not have a host-provided random
driver; KVM for example does.

It might be helpful to document which parts need randomness, eg I
imagine many filesystems do not.

> Note, lack of platform randomness can be problematic especially on
> short-lived guests, but not sure how we can produce something we don't have.

RDRAND support in NetBSD would help for amd64 for hardware that supports it.

Justin

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