Date:   Mon, 5 Oct 2020 20:24:00 +0300
From:   Diana Craciun OSS <diana.craciun@....nxp.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     kvm@...r.kernel.org, bharatb.linux@...il.com,
        linux-kernel@...r.kernel.org, eric.auger@...hat.com,
        Bharat Bhushan <Bharat.Bhushan@....com>
Subject: Re: [PATCH v5 02/10] vfio/fsl-mc: Scan DPRC objects on vfio-fsl-mc
 driver bind

On 10/2/2020 8:24 PM, Alex Williamson wrote:
> On Tue, 29 Sep 2020 12:03:31 +0300
> Diana Craciun <diana.craciun@....nxp.com> wrote:
> 
>> The DPRC (Data Path Resource Container) device is a bus device and has
>> child devices attached to it. When the vfio-fsl-mc driver is probed
>> the DPRC is scanned and the child devices discovered and initialized.
>>
>> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@....com>
>> Signed-off-by: Diana Craciun <diana.craciun@....nxp.com>
>> ---
>>   drivers/vfio/fsl-mc/vfio_fsl_mc.c         | 90 +++++++++++++++++++++++
>>   drivers/vfio/fsl-mc/vfio_fsl_mc_private.h |  1 +
>>   2 files changed, 91 insertions(+)
>>
>> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
>> index a7a483a1e90b..ba44d6d01cc9 100644
>> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
>> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
>> @@ -15,6 +15,8 @@
>>   
>>   #include "vfio_fsl_mc_private.h"
>>   
>> +static struct fsl_mc_driver vfio_fsl_mc_driver;
>> +
>>   static int vfio_fsl_mc_open(void *device_data)
>>   {
>>   	if (!try_module_get(THIS_MODULE))
>> @@ -84,6 +86,79 @@ static const struct vfio_device_ops vfio_fsl_mc_ops = {
>>   	.mmap		= vfio_fsl_mc_mmap,
>>   };
>>   
>> +static int vfio_fsl_mc_bus_notifier(struct notifier_block *nb,
>> +				    unsigned long action, void *data)
>> +{
>> +	struct vfio_fsl_mc_device *vdev = container_of(nb,
>> +					struct vfio_fsl_mc_device, nb);
>> +	struct device *dev = data;
>> +	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
>> +	struct fsl_mc_device *mc_cont = to_fsl_mc_device(mc_dev->dev.parent);
>> +
>> +	if (action == BUS_NOTIFY_ADD_DEVICE &&
>> +	    vdev->mc_dev == mc_cont) {
>> +		mc_dev->driver_override = kasprintf(GFP_KERNEL, "%s",
>> +						    vfio_fsl_mc_ops.name);
>> +		if (!mc_dev->driver_override)
>> +			dev_warn(dev, "VFIO_FSL_MC: Setting driver override for device in dprc %s failed\n",
>> +			     dev_name(&mc_cont->dev));
>> +		else
>> +			dev_info(dev, "VFIO_FSL_MC: Setting driver override for device in dprc %s\n",
>> +			 dev_name(&mc_cont->dev));
> 
> Nit, some whitespace inconsistencies on the second line of each of
> these.  I can fixup on commit if we don't find anything else worth a
> respin.
> 
>> +	} else if (action == BUS_NOTIFY_BOUND_DRIVER &&
>> +		vdev->mc_dev == mc_cont) {
>> +		struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(dev->driver);
>> +
>> +		if (mc_drv && mc_drv != &vfio_fsl_mc_driver)
>> +			dev_warn(dev, "VFIO_FSL_MC: Object %s bound to driver %s while DPRC bound to vfio-fsl-mc\n",
>> +				 dev_name(dev), mc_drv->driver.name);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int vfio_fsl_mc_init_device(struct vfio_fsl_mc_device *vdev)
>> +{
>> +	struct fsl_mc_device *mc_dev = vdev->mc_dev;
>> +	int ret;
>> +
>> +	/* Non-dprc devices share mc_io from parent */
>> +	if (!is_fsl_mc_bus_dprc(mc_dev)) {
>> +		struct fsl_mc_device *mc_cont = to_fsl_mc_device(mc_dev->dev.parent);
>> +
>> +		mc_dev->mc_io = mc_cont->mc_io;
>> +		return 0;
>> +	}
>> +
>> +	vdev->nb.notifier_call = vfio_fsl_mc_bus_notifier;
>> +	ret = bus_register_notifier(&fsl_mc_bus_type, &vdev->nb);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* open DPRC, allocate a MC portal */
>> +	ret = dprc_setup(mc_dev);
>> +	if (ret) {
>> +		dev_err(&mc_dev->dev, "VFIO_FSL_MC: Failed to setup DPRC (%d)\n", ret);
>> +		goto out_nc_unreg;
>> +	}
>> +
>> +	ret = dprc_scan_container(mc_dev, false);
>> +	if (ret) {
>> +		dev_err(&mc_dev->dev, "VFIO_FSL_MC: Container scanning failed (%d)\n", ret);
>> +		goto out_dprc_cleanup;
>> +	}
> 
> If I understand this correctly, we've setup the bus notifier to write
> the driver override as each sub-devices appear on the bus from this
> scan.  When non-dprc devices are removed below, it appears we remove all
> their sub-devices.  Is there a chance here that an error from the scan
> leaves residual sub-devices, ie. should we proceed the below
> dprc_cleanup() with a call to dprc_remove_devices() to be certain none
> remain?  Thanks,
> 
> Alex

Right, we should call dprc_remove_devices as well. I will respin another 
version.

> 
> 
>> +
>> +	return 0;
>> +
>> +out_dprc_cleanup:
>> +	dprc_cleanup(mc_dev);
>> +out_nc_unreg:
>> +	bus_unregister_notifier(&fsl_mc_bus_type, &vdev->nb);
>> +	vdev->nb.notifier_call = NULL;
>> +
>> +	return ret;
>> +}
>> +
>>   static int vfio_fsl_mc_probe(struct fsl_mc_device *mc_dev)
>>   {
>>   	struct iommu_group *group;
>> @@ -110,8 +185,15 @@ static int vfio_fsl_mc_probe(struct fsl_mc_device *mc_dev)
>>   		dev_err(dev, "VFIO_FSL_MC: Failed to add to vfio group\n");
>>   		goto out_group_put;
>>   	}
>> +
>> +	ret = vfio_fsl_mc_init_device(vdev);
>> +	if (ret)
>> +		goto out_group_dev;
>> +
>>   	return 0;
>>   
>> +out_group_dev:
>> +	vfio_del_group_dev(dev);
>>   out_group_put:
>>   	vfio_iommu_group_put(group, dev);
>>   	return ret;
>> @@ -126,6 +208,14 @@ static int vfio_fsl_mc_remove(struct fsl_mc_device *mc_dev)
>>   	if (!vdev)
>>   		return -EINVAL;
>>   
>> +	if (is_fsl_mc_bus_dprc(mc_dev)) {
>> +		dprc_remove_devices(mc_dev, NULL, 0);
>> +		dprc_cleanup(mc_dev);
>> +	}
>> +
>> +	if (vdev->nb.notifier_call)
>> +		bus_unregister_notifier(&fsl_mc_bus_type, &vdev->nb);
>> +
>>   	vfio_iommu_group_put(mc_dev->dev.iommu_group, dev);
>>   
>>   	return 0;
>> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
>> index e79cc116f6b8..37d61eaa58c8 100644
>> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
>> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc_private.h
>> @@ -9,6 +9,7 @@
>>   
>>   struct vfio_fsl_mc_device {
>>   	struct fsl_mc_device		*mc_dev;
>> +	struct notifier_block        nb;
>>   };
>>   
>>   #endif /* VFIO_FSL_MC_PRIVATE_H */
> 

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