2017-11-03 09:58:01

by Jim Quigley

[permalink] [raw]
Subject: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume

The patch for

commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
Author: Amit Shah <[email protected]>
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 <[email protected]>
Signed-off-by: Jim Quigley <[email protected]>
---
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


Subject: 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 <[email protected]> wrote:
> The patch for
>
> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
> Author: Amit Shah <[email protected]>
> 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 <[email protected]>
> Signed-off-by: Jim Quigley <[email protected]>
> ---
> 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

2017-11-03 14:41:24

by Jim Quigley

[permalink] [raw]
Subject: 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 <[email protected]> wrote:
>> The patch for
>>
>> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
>> Author: Amit Shah <[email protected]>
>> 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 <[email protected]>
>> Signed-off-by: Jim Quigley <[email protected]>
>> ---
>> 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

Subject: 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 <[email protected]> wrote:
> The patch for
>
> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
> Author: Amit Shah <[email protected]>
> 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 <[email protected]>
> Signed-off-by: Jim Quigley <[email protected]>
> ---
> 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 <[email protected]>

Regards,
PrasannaKumar

2017-11-06 07:09:59

by Herbert Xu

[permalink] [raw]
Subject: Re: virtio:rng: Virtio RNG devices need to be re-registered after suspend/resume

On Fri, Nov 03, 2017 at 09:57:21AM +0000, Jim Quigley wrote:
> The patch for
>
> commit: 5c06273401f2eb7b290cadbae18ee00f8f65e893
> Author: Amit Shah <[email protected]>
> 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 <[email protected]>
> Signed-off-by: Jim Quigley <[email protected]>

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Subject: 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 <[email protected]> wrote:
> On Fri, Nov 03, 2017 at 09:57:21AM +0000, 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

2017-11-07 03:37:22

by Herbert Xu

[permalink] [raw]
Subject: 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 <[email protected]> wrote:
> > On Fri, Nov 03, 2017 at 09:57:21AM +0000, 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 <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt