linux-kernel - Re: [RFC 5/9] VFIO: Extend external user API

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Date:	Wed, 27 Aug 2014 17:20:46 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	eric.auger@...com, christoffer.dall@...aro.org,
	marc.zyngier@....com, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	joel.schopp@....com, kim.phillips@...escale.com,
	linux-kernel@...r.kernel.org, patches@...aro.org,
	will.deacon@....com, a.motakis@...tualopensystems.com,
	a.rigo@...tualopensystems.com, john.liuli@...wei.com
Subject: Re: [RFC 5/9] VFIO: Extend external user API

On 08/26/2014 09:02 PM, Alex Williamson wrote:
> On Mon, 2014-08-25 at 15:27 +0200, Eric Auger wrote:
>> New functions are added to be called from ARM KVM-VFIO device.
>>
>> - vfio_device_get_external_user enables to get a vfio device from
>>   its fd
>> - vfio_device_put_external_user puts the vfio device
>> - vfio_external_get_type enables to retrieve the type of the device
>>   (PCI or platform)
>> - vfio_external_get_base_device enables to get the
>>   struct device*, useful to access the platform_device
>>
>> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>> ---
>>  drivers/vfio/vfio.c  | 35 +++++++++++++++++++++++++++++++++++
>>  include/linux/vfio.h |  4 ++++
>>  2 files changed, 39 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
>> index 8e84471..c93b9e4 100644
>> --- a/drivers/vfio/vfio.c
>> +++ b/drivers/vfio/vfio.c
>> @@ -1401,6 +1401,41 @@ void vfio_group_put_external_user(struct vfio_group *group)
>>  }
>>  EXPORT_SYMBOL_GPL(vfio_group_put_external_user);
>>  
>> +struct vfio_device *vfio_device_get_external_user(struct file *filep)
>> +{
>> +	struct vfio_device *vdev = filep->private_data;
>> +
>> +	if (filep->f_op != &vfio_device_fops)
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	vfio_device_get(vdev);
>> +	return vdev;
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_device_get_external_user);
>> +
>> +void vfio_device_put_external_user(struct vfio_device *vdev)
>> +{
>> +	vfio_device_put(vdev);
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_device_put_external_user);
>> +
>> +int vfio_external_get_type(struct vfio_device *vdev)
>> +{
>> +	if (!strcmp(vdev->ops->name,  "vfio-platform"))
>> +		return VFIO_DEVICE_FLAGS_PLATFORM;
>> +	else if (!strcmp(vdev->ops->name,  "vfio-pci"))
>> +		return VFIO_DEVICE_FLAGS_PCI;
>> +	else
>> +		return -EINVAL;
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_external_get_type);
> 
> Returning the bit of the flag we use in get_device_info looks rather
> sloppy here.  Should we define a new enum for use with this?  Actually,
> is this interface even necessary?  If we can get the struct device then
> we can get the bus_type and keep vfio out of this.

thanks for the nit. I will try to get rid of it using it.
> 
> For both of these last two, I like to use the convention that where
> there is a "get" there is a matching "put".  These aren't reference
> counting anything, so let's not use get in the name.

I will rename.

Thanks

Eric
> 
>> +
>> +struct device *vfio_external_get_base_device(struct vfio_device *vdev)
>> +{
>> +	return vdev->dev;
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_external_get_base_device);
>> +
> 
> Looks almost too simple, but reviewing the object lifecycles, this all
> looks safe.  Thanks,
> 
> Alex
> 
>>  int vfio_external_user_iommu_id(struct vfio_group *group)
>>  {
>>  	return iommu_group_id(group->iommu_group);
>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index ffe04ed..19e98eb 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -99,6 +99,10 @@ extern void vfio_group_put_external_user(struct vfio_group *group);
>>  extern int vfio_external_user_iommu_id(struct vfio_group *group);
>>  extern long vfio_external_check_extension(struct vfio_group *group,
>>  					  unsigned long arg);
>> +extern struct vfio_device *vfio_device_get_external_user(struct file *filep);
>> +extern void vfio_device_put_external_user(struct vfio_device *vdev);
>> +extern int vfio_external_get_type(struct vfio_device *vdev);
>> +extern struct device *vfio_external_get_base_device(struct vfio_device *vdev);
>>  
>>  struct pci_dev;
>>  #ifdef CONFIG_EEH
> 
> 
> 

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