linux-kernel - Re: [PATCH] mdev: Send uevents around parent device registration

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Date:   Thu, 27 Jun 2019 19:42:32 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     Cornelia Huck <cohuck@...hat.com>
CC:     Alex Williamson <alex.williamson@...hat.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mdev: Send uevents around parent device registration



On 6/27/2019 1:51 PM, Cornelia Huck wrote:
> On Thu, 27 Jun 2019 00:33:59 +0530
> Kirti Wankhede <kwankhede@...dia.com> wrote:
> 
>> On 6/26/2019 11:35 PM, Alex Williamson wrote:
>>> On Wed, 26 Jun 2019 23:23:00 +0530
>>> Kirti Wankhede <kwankhede@...dia.com> wrote:
>>>   
>>>> On 6/26/2019 7:57 PM, Alex Williamson wrote:  
>>>>> This allows udev to trigger rules when a parent device is registered
>>>>> or unregistered from mdev.
>>>>>
>>>>> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
>>>>> ---
>>>>>  drivers/vfio/mdev/mdev_core.c |   10 ++++++++--
>>>>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>>>>> index ae23151442cb..ecec2a3b13cb 100644
>>>>> --- a/drivers/vfio/mdev/mdev_core.c
>>>>> +++ b/drivers/vfio/mdev/mdev_core.c
>>>>> @@ -146,6 +146,8 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
>>>>>  {
>>>>>  	int ret;
>>>>>  	struct mdev_parent *parent;
>>>>> +	char *env_string = "MDEV_STATE=registered";
>>>>> +	char *envp[] = { env_string, NULL };
>>>>>  
>>>>>  	/* check for mandatory ops */
>>>>>  	if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
>>>>> @@ -196,7 +198,8 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
>>>>>  	list_add(&parent->next, &parent_list);
>>>>>  	mutex_unlock(&parent_list_lock);
>>>>>  
>>>>> -	dev_info(dev, "MDEV: Registered\n");
>>>>> +	kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
>>>>> +    
>>>>
>>>> Its good to have udev event, but don't remove debug print from dmesg.
>>>> Same for unregister.  
>>>
>>> Who consumes these?  They seem noisy.  Thanks,
>>>   
>>
>> I don't think its noisy, its more of logging purpose. This is seen in
>> kernel log only when physical device is registered to mdev.
> 
> Yes; but why do you want to log success? If you need to log it
> somewhere, wouldn't a trace event be a much better choice?
> 

Trace events are not always collected in production environment, there
kernel log helps.

Thanks,
Kirti