Linux Virtualization - Jul 2014 - [PATCH v2 1/2] hwrng: fetch randomness only after device init

On Sat, Jul 05, 2014 at 11:04:52AM +0530, Amit Shah
wrote:
> Commit d9e7972619334 "hwrng: add randomness to system from rng
sources"
> added a call to rng_get_data() from the hwrng_register() function.
> However, some rng devices need initialization before data can be read
> from them.
> 
> This commit makes the call to rng_get_data() depend on no init fn
> pointer being registered by the device.  If an init function is
> registered, this call is made after device init.
> 
> CC: Kees Cook <keescook at chromium.org>
> CC: Jason Cooper <jason at lakedaemon.net>
> CC: Herbert Xu <herbert at gondor.apana.org.au>
> CC: <stable at vger.kernel.org> # For v3.15+
> Signed-off-by: Amit Shah <amit.shah at redhat.com>
> ---
>  drivers/char/hw_random/core.c | 31 +++++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
Thanks for cleaning this up!

Reviewed-by: Jason Cooper <jason at lakedaemon.net>

thx,

Jason.

On (Wed) 09 Jul 2014 [07:53:17], Jason Cooper wrote:
> On Sat, Jul 05, 2014 at 11:04:52AM +0530, Amit Shah wrote:
> > Commit d9e7972619334 "hwrng: add randomness to system from rng
sources"
> > added a call to rng_get_data() from the hwrng_register() function.
> > However, some rng devices need initialization before data can be read
> > from them.
> > 
> > This commit makes the call to rng_get_data() depend on no init fn
> > pointer being registered by the device.  If an init function is
> > registered, this call is made after device init.
> > 
> > CC: Kees Cook <keescook at chromium.org>
> > CC: Jason Cooper <jason at lakedaemon.net>
> > CC: Herbert Xu <herbert at gondor.apana.org.au>
> > CC: <stable at vger.kernel.org> # For v3.15+
> > Signed-off-by: Amit Shah <amit.shah at redhat.com>
> > ---
> >  drivers/char/hw_random/core.c | 31 +++++++++++++++++++++++++------
> >  1 file changed, 25 insertions(+), 6 deletions(-)
> 
> Thanks for cleaning this up!
Thanks!

Any thoughts on the follow-up patch posted later that resolves some of
the weirdness in init?

		Amit

On Wed, Jul 09, 2014 at 06:38:22PM +0530, Amit Shah
wrote:
> On (Wed) 09 Jul 2014 [07:53:17], Jason Cooper wrote:
> > On Sat, Jul 05, 2014 at 11:04:52AM +0530, Amit Shah wrote:
> > > Commit d9e7972619334 "hwrng: add randomness to system from
rng sources"
> > > added a call to rng_get_data() from the hwrng_register()
function.
> > > However, some rng devices need initialization before data can be
read
> > > from them.
> > > 
> > > This commit makes the call to rng_get_data() depend on no init fn
> > > pointer being registered by the device.  If an init function is
> > > registered, this call is made after device init.
> > > 
> > > CC: Kees Cook <keescook at chromium.org>
> > > CC: Jason Cooper <jason at lakedaemon.net>
> > > CC: Herbert Xu <herbert at gondor.apana.org.au>
> > > CC: <stable at vger.kernel.org> # For v3.15+
> > > Signed-off-by: Amit Shah <amit.shah at redhat.com>
> > > ---
> > >  drivers/char/hw_random/core.c | 31
+++++++++++++++++++++++++------
> > >  1 file changed, 25 insertions(+), 6 deletions(-)
> > 
> > Thanks for cleaning this up!
> 
> Thanks!
> 
> Any thoughts on the follow-up patch posted later that resolves some of
> the weirdness in init?
hmm, I'd rather see an init function for virtio-rng that checks the bit
and returns 0 or -EAGAIN.  With your proposed change, you would get
hangs again.

thx,

Jason.