On Mon, Jul 14, 2014 at 10:05:19AM +0530, Amit Shah wrote:
> Some RNG devices may not be ready to give early randomness at probe()
> time, and hence lose out on the opportunity to contribute to system
> randomness at boot- or device hotplug- time.
>
> This commit schedules a delayed work item for such devices, and fetches
> early randomness after a delay. Currently the delay is 500ms, which is
> enough for the lone device that needs such treatment: virtio-rng.
>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> CC: Jason Cooper <jason@xxxxxxxxxxxxxx>
> CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
> ---
> drivers/char/hw_random/core.c | 20 +++++++++++++++++++-
> include/linux/hw_random.h | 8 ++++++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index c4419ea..2a765fd 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -63,7 +63,7 @@ static size_t rng_buffer_size(void)
> return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
> }
>
> -static void add_early_randomness(struct hwrng *rng)
> +static void get_early_randomness(struct hwrng *rng)
> {
> unsigned char bytes[16];
> int bytes_read;
> @@ -79,6 +79,21 @@ static void add_early_randomness(struct hwrng *rng)
> add_device_randomness(bytes, bytes_read);
> }
>
> +static void sched_init_random(struct work_struct *work)
> +{
> + struct hwrng *rng = container_of(work, struct hwrng, dwork.work);
> +
> + get_early_randomness(rng);
> +}
> +
> +static void add_early_randomness(struct hwrng *rng)
The add/get naming seems awkward in the above hunks.
> +{
> + if (!(rng->flags & HWRNG_DELAY_READ_AT_INIT))
> + return get_early_randomness(rng);
> +
> + schedule_delayed_work(&rng->dwork, msecs_to_jiffies(500));
> +}
> +
Perhaps instead of rng->flags and a hardcoded delay, we could have
rng->seed_delay = msecs_to_jiffies(500) in virtio-rng? Then you can
just call unconditionally:
schedule_delayed_work(&rng->dwork, rng->seed_delay);
I think that would be a more extensible solution should other drivers
show up with the same issue.
thx,
Jason.
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
