Re: [PATCH 1/9] dmaengine: idxd: Fix lockdep warnings when calling idxd_device_config()

[Vinicius Costa Gomes <vinicius.gomes@intel.com>]

Dave Jiang <dave.jiang@intel.com> writes:

> On 8/4/25 6:27 PM, Vinicius Costa Gomes wrote:
>> idxd_device_config() should only be called with idxd->dev_lock held.
>> Hold the lock to the calls that were missing.
>> 
>> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>
> Patch looks fine. What about doing something like this:
>
> ---
>
> diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
> index 5cf419fe6b46..06c182ec3c04 100644
> --- a/drivers/dma/idxd/device.c
> +++ b/drivers/dma/idxd/device.c
> @@ -1103,11 +1103,15 @@ static int idxd_wqs_setup(struct idxd_device *idxd)
>  	return 0;
>  }
>  
> -int idxd_device_config(struct idxd_device *idxd)
> +int idxd_device_config_locked(struct idxd_device *idxd)
>  {
>  	int rc;
>  
>  	lockdep_assert_held(&idxd->dev_lock);
> +
> +	if (!test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags))
> +		return -EPERM;
> +
>  	rc = idxd_wqs_setup(idxd);
>  	if (rc < 0)
>  		return rc;
> @@ -1129,6 +1133,12 @@ int idxd_device_config(struct idxd_device *idxd)
>  	return 0;
>  }
>  
> +int idxd_device_config(struct idxd_device *idxd)
> +{
> +	guard(spinlock)(&idxd->dev_lock);
> +	return idxd_device_config_locked(idxd);
> +}
> +

This gave me the idea that moving the lock to idxd_device_config() might
be a better idea. As the _locked() variant doesn't seem to be used, I
don't see why we should keep it around. Will give it a try and see how
it looks.

Thanks.

>  static int idxd_wq_load_config(struct idxd_wq *wq)
>  {
>  	struct idxd_device *idxd = wq->idxd;
> @@ -1434,11 +1444,7 @@ int idxd_drv_enable_wq(struct idxd_wq *wq)
>  		}
>  	}
>  
> -	rc = 0;
> -	spin_lock(&idxd->dev_lock);
> -	if (test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags))
> -		rc = idxd_device_config(idxd);
> -	spin_unlock(&idxd->dev_lock);
> +	rc = idxd_device_config(idxd);
>  	if (rc < 0) {
>  		dev_dbg(dev, "Writing wq %d config failed: %d\n", wq->id, rc);
>  		goto err;
> @@ -1521,7 +1527,7 @@ EXPORT_SYMBOL_NS_GPL(idxd_drv_disable_wq, "IDXD");
>  int idxd_device_drv_probe(struct idxd_dev *idxd_dev)
>  {
>  	struct idxd_device *idxd = idxd_dev_to_idxd(idxd_dev);
> -	int rc = 0;
> +	int rc;
>  
>  	/*
>  	 * Device should be in disabled state for the idxd_drv to load. If it's in
> @@ -1534,10 +1540,7 @@ int idxd_device_drv_probe(struct idxd_dev *idxd_dev)
>  	}
>  
>  	/* Device configuration */
> -	spin_lock(&idxd->dev_lock);
> -	if (test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags))
> -		rc = idxd_device_config(idxd);
> -	spin_unlock(&idxd->dev_lock);
> +	rc = idxd_device_config(idxd);
>  	if (rc < 0)
>  		return -ENXIO;
>  
> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
> index 74e6695881e6..f15bc2281c6b 100644
> --- a/drivers/dma/idxd/idxd.h
> +++ b/drivers/dma/idxd/idxd.h
> @@ -760,6 +760,7 @@ int idxd_device_disable(struct idxd_device *idxd);
>  void idxd_device_reset(struct idxd_device *idxd);
>  void idxd_device_clear_state(struct idxd_device *idxd);
>  int idxd_device_config(struct idxd_device *idxd);
> +int idxd_device_config_locked(struct idxd_device *idxd);
>  void idxd_device_drain_pasid(struct idxd_device *idxd, int pasid);
>  int idxd_device_load_config(struct idxd_device *idxd);
>  int idxd_device_request_int_handle(struct idxd_device *idxd, int idx, int *handle,
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 80355d03004d..193b9282e30f 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -1091,12 +1091,10 @@ static void idxd_reset_done(struct pci_dev *pdev)
>  	idxd_device_config_restore(idxd, idxd->idxd_saved);
>  
>  	/* Re-configure IDXD device if allowed. */
> -	if (test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags)) {
> -		rc = idxd_device_config(idxd);
> -		if (rc < 0) {
> -			dev_err(dev, "HALT: %s config fails\n", idxd_name);
> -			goto out;
> -		}
> +	rc = idxd_device_config(idxd);
> +	if (rc < 0) {
> +		dev_err(dev, "HALT: %s config fails\n", idxd_name);
> +		goto out;
>  	}
>  
>  	/* Bind IDXD device to driver. */
>
>
>> ---
>>  drivers/dma/idxd/init.c | 2 ++
>>  drivers/dma/idxd/irq.c  | 2 ++
>>  2 files changed, 4 insertions(+)
>> 
>> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
>> index 35bdefd3728bb851beb0f235fae7c6d71bd59239..d828d352ab008127e5e442e7072c9d5df0f2c6cf 100644
>> --- a/drivers/dma/idxd/init.c
>> +++ b/drivers/dma/idxd/init.c
>> @@ -1091,7 +1091,9 @@ static void idxd_reset_done(struct pci_dev *pdev)
>>  
>>  	/* Re-configure IDXD device if allowed. */
>>  	if (test_bit(IDXD_FLAG_CONFIGURABLE, &idxd->flags)) {
>> +		spin_lock(&idxd->dev_lock);
>>  		rc = idxd_device_config(idxd);
>> +		spin_unlock(&idxd->dev_lock);
>>  		if (rc < 0) {
>>  			dev_err(dev, "HALT: %s config fails\n", idxd_name);
>>  			goto out;
>> diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
>> index 1107db3ce0a3a65246bd0d9b1f96e99c9fa3def6..74059fe43fafeb930f58db21d3824f62b095b968 100644
>> --- a/drivers/dma/idxd/irq.c
>> +++ b/drivers/dma/idxd/irq.c
>> @@ -36,7 +36,9 @@ static void idxd_device_reinit(struct work_struct *work)
>>  	int rc, i;
>>  
>>  	idxd_device_reset(idxd);
>> +	spin_lock(&idxd->dev_lock);
>>  	rc = idxd_device_config(idxd);
>> +	spin_unlock(&idxd->dev_lock);
>>  	if (rc < 0)
>>  		goto out;
>>  
>> 
>

-- 
Vinicius