Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
On Tue, Nov 07, 2017 at 08:44:17AM +0530, PrasannaKumar Muralidharan wrote: > Hi Herbert, > > On 6 November 2017 at 12:39, Herbert Xu wrote: > > On Fri, Nov 03, 2017 at 09:57:21AM +, Jim Quigley wrote: > >> moved the call to hwrng_register() out of the probe routine into the scan > >> routine. We need to call hwrng_register() after a suspend/restore cycle > >> to re-register the device, but the scan function is not invoked for the > >> restore. Add the call to hwrng_register() to virtio_restore(). > > > > Patch applied. Thanks. > > My rb tag is missing in the commit. That's because you didn't start it on a new line. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
Hi Herbert, On 6 November 2017 at 12:39, Herbert Xu wrote: > On Fri, Nov 03, 2017 at 09:57:21AM +, Jim Quigley wrote: >> moved the call to hwrng_register() out of the probe routine into the scan >> routine. We need to call hwrng_register() after a suspend/restore cycle >> to re-register the device, but the scan function is not invoked for the >> restore. Add the call to hwrng_register() to virtio_restore(). > > Patch applied. Thanks. My rb tag is missing in the commit. Regards, PrasannaKumar
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
On Fri, Nov 03, 2017 at 09:57:21AM +, Jim Quigley wrote: > The patch for > > commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893 > Author: Amit Shah > Date: Sun Jul 27 07:34:01 2014 +0930 > > virtio: rng: delay hwrng_register() till driver is ready > > moved the call to hwrng_register() out of the probe routine into the scan > routine. We need to call hwrng_register() after a suspend/restore cycle > to re-register the device, but the scan function is not invoked for the > restore. Add the call to hwrng_register() to virtio_restore(). > > Reviewed-by: Liam Merwick > Signed-off-by: Jim Quigley Patch applied. Thanks. -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
Jim,
Minor comment below.
On 3 November 2017 at 15:27, Jim Quigley wrote:
> The patch for
>
> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
> Author: Amit Shah
> Date: Sun Jul 27 07:34:01 2014 +0930
>
> virtio: rng: delay hwrng_register() till driver is ready
>
> moved the call to hwrng_register() out of the probe routine into the scan
> routine. We need to call hwrng_register() after a suspend/restore cycle
> to re-register the device, but the scan function is not invoked for the
> restore. Add the call to hwrng_register() to virtio_restore().
>
> Reviewed-by: Liam Merwick
> Signed-off-by: Jim Quigley
> ---
> drivers/char/hw_random/virtio-rng.c | 21 -
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/hw_random/virtio-rng.c
> b/drivers/char/hw_random/virtio-rng.c
> index 3fa2f8a..b89df66 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -184,7 +184,26 @@ static int virtrng_freeze(struct virtio_device *vdev)
>
> static int virtrng_restore(struct virtio_device *vdev)
> {
> - return probe_common(vdev);
> + int err;
> +
> + err = probe_common(vdev);
> + if (!err) {
> + struct virtrng_info *vi = vdev->priv;
> +
> + /*
> +* Set hwrng_removed to ensure that virtio_read()
> +* does not block waiting for data before the
> +* registration is complete.
> +*/
> + vi->hwrng_removed = true;
Hwrng core does not call read method till hwrng_register has finished.
Is this really required? I think it has no effect.
> + err = hwrng_register(&vi->hwrng);
> + if (!err) {
> + vi->hwrng_register_done = true;
> + vi->hwrng_removed = false;
> + }
> + }
> +
> + return err;
> }
> #endif
>
> --
> 1.8.3.1
>
I am fine with this change as is. Reviewed-by: PrasannaKumar
Muralidharan
Regards,
PrasannaKumar
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
Hi Jim, Have second thoughts on this. On 3 November 2017 at 20:55, PrasannaKumar Muralidharan wrote: >> >> It would be cleaner to just get rid of probe_common() altogether in that >> case, and do whatever >> needs to be done in virtrng_probe()/virtrng_restore() respectively, but > > That's correct. > >> I didn't want to change code >> affecting the normal probe path as well as suspend/resume. Is it OK to >> leave it that way to avoid >> the more extensive changes ? > > Personally I would prefer to do the cleaner way. It is up to the > virtio and hwrng maintainer. You are trying to restore the status quo of the driver that was before the commit 5c06273401. It is really important and valid. The driver's suspend/resume code is not in best shape but that is not what you are trying to solve. I am fine with this change. Regards, PrasannaKumar
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
On 03/11/2017 13:06, PrasannaKumar Muralidharan wrote:
Hi Jim,
On 3 November 2017 at 15:27, Jim Quigley wrote:
The patch for
commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
Author: Amit Shah
Date: Sun Jul 27 07:34:01 2014 +0930
virtio: rng: delay hwrng_register() till driver is ready
moved the call to hwrng_register() out of the probe routine into the scan
routine. We need to call hwrng_register() after a suspend/restore cycle
to re-register the device, but the scan function is not invoked for the
restore. Add the call to hwrng_register() to virtio_restore().
Reviewed-by: Liam Merwick
Signed-off-by: Jim Quigley
---
drivers/char/hw_random/virtio-rng.c | 21 -
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/virtio-rng.c
b/drivers/char/hw_random/virtio-rng.c
index 3fa2f8a..b89df66 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -184,7 +184,26 @@ static int virtrng_freeze(struct virtio_device *vdev)
static int virtrng_restore(struct virtio_device *vdev)
{
- return probe_common(vdev);
+ int err;
+
+ err = probe_common(vdev);
+ if (!err) {
+ struct virtrng_info *vi = vdev->priv;
+
+ /*
+* Set hwrng_removed to ensure that virtio_read()
+* does not block waiting for data before the
+* registration is complete.
+*/
+ vi->hwrng_removed = true;
+ err = hwrng_register(&vi->hwrng);
+ if (!err) {
+ vi->hwrng_register_done = true;
+ vi->hwrng_removed = false;
+ }
+ }
+
+ return err;
}
#endif
--
1.8.3.1
This patch makes me wonder why hwrng_unregister is required in
virtrng_freeze. Looks strange and unusual. May be that is not required
and it can be removed. If it is required can you please add a comment
on why it is required?
The reason it's required is because the virtrng_restore() uses
probe_common() which allocates
a new virtrng_info struct, changing the devices private pointer .
This virtrng struct is used in
hwrng_register() to set the current RNG etc. If we don't
unregister/re-register then we would
need to split probe_common() to avoid
vi = kzalloc(sizeof(struct virtrng_info), GFP_KERNEL);
overwriting vdev->priv on a restore.
It would be cleaner to just get rid of probe_common() altogether in
that case, and do whatever
needs to be done in virtrng_probe()/virtrng_restore() respectively,
but I didn't want to change code
affecting the normal probe path as well as suspend/resume. Is it OK
to leave it that way to avoid
the more extensive changes ?
thanks
regards
Jim Q.
Thanks,
PrasannaKumar
Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume
Hi Jim,
On 3 November 2017 at 15:27, Jim Quigley wrote:
> The patch for
>
> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
> Author: Amit Shah
> Date: Sun Jul 27 07:34:01 2014 +0930
>
> virtio: rng: delay hwrng_register() till driver is ready
>
> moved the call to hwrng_register() out of the probe routine into the scan
> routine. We need to call hwrng_register() after a suspend/restore cycle
> to re-register the device, but the scan function is not invoked for the
> restore. Add the call to hwrng_register() to virtio_restore().
>
> Reviewed-by: Liam Merwick
> Signed-off-by: Jim Quigley
> ---
> drivers/char/hw_random/virtio-rng.c | 21 -
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/hw_random/virtio-rng.c
> b/drivers/char/hw_random/virtio-rng.c
> index 3fa2f8a..b89df66 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -184,7 +184,26 @@ static int virtrng_freeze(struct virtio_device *vdev)
>
> static int virtrng_restore(struct virtio_device *vdev)
> {
> - return probe_common(vdev);
> + int err;
> +
> + err = probe_common(vdev);
> + if (!err) {
> + struct virtrng_info *vi = vdev->priv;
> +
> + /*
> +* Set hwrng_removed to ensure that virtio_read()
> +* does not block waiting for data before the
> +* registration is complete.
> +*/
> + vi->hwrng_removed = true;
> + err = hwrng_register(&vi->hwrng);
> + if (!err) {
> + vi->hwrng_register_done = true;
> + vi->hwrng_removed = false;
> + }
> + }
> +
> + return err;
> }
> #endif
>
> --
> 1.8.3.1
>
This patch makes me wonder why hwrng_unregister is required in
virtrng_freeze. Looks strange and unusual. May be that is not required
and it can be removed. If it is required can you please add a comment
on why it is required?
Thanks,
PrasannaKumar
