Re: [PATCH v12 05/22] vfio iommu: Added pin and unpin callback functions to vfio_iommu_driver_ops

[Kirti Wankhede]

On 11/15/2016 1:13 AM, Alex Williamson wrote:
> On Mon, 14 Nov 2016 21:12:19 +0530
> Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
> 
>> Added APIs for pining and unpining set of pages. These call back into
>> backend iommu module to actually pin and unpin pages.
>> Added two new callback functions to struct vfio_iommu_driver_ops. Backend
>> IOMMU module that supports pining and unpinning pages for mdev devices
>> should provide these functions.
>>
>> Renamed static functions in vfio_type1_iommu.c to resolve conflicts
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
>> Signed-off-by: Neo Jia <cjia@xxxxxxxxxx>
>> Change-Id: Ia7417723aaae86bec2959ad9ae6c2915ddd340e0
>> ---
>>  drivers/vfio/vfio.c             | 103 ++++++++++++++++++++++++++++++++++++++++
>>  drivers/vfio/vfio_iommu_type1.c |  20 ++++----
>>  include/linux/vfio.h            |  12 ++++-
>>  3 files changed, 124 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
>> index 2e83bdf007fe..7dcfbca2016a 100644
>> --- a/drivers/vfio/vfio.c
>> +++ b/drivers/vfio/vfio.c
>> @@ -1799,6 +1799,109 @@ void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
>>  }
>>  EXPORT_SYMBOL_GPL(vfio_info_cap_shift);
>>  
>> +
>> +/*
>> + * Pin a set of guest PFNs and return their associated host PFNs for local
>> + * domain only.
>> + * @dev [in] : device
>> + * @user_pfn [in]: array of user/guest PFNs to be unpinned. Number of user/guest
>> + *		  PFNs should not be greater than PAGE_SIZE.
>> + * @npage [in] :count of elements in array.  This count should not be greater
>> + *		than PAGE_SIZE.
>> + * @prot [in] : protection flags
>> + * @phys_pfn[out] : array of host PFNs
>> + * Return error or number of pages pinned.
>> + */
>> +int vfio_pin_pages(struct device *dev, unsigned long *user_pfn, int npage,
>> +		   int prot, unsigned long *phys_pfn)
>> +{
>> +	struct vfio_container *container;
>> +	struct vfio_group *group;
>> +	struct vfio_iommu_driver *driver;
>> +	int ret;
>> +
>> +	if (!dev || !user_pfn || !phys_pfn || !npage)
>> +		return -EINVAL;
>> +
>> +	if (npage >= PAGE_SIZE)
>> +		return -E2BIG;
> 
> This misses the point of using PAGE_SIZE.  The concern is that
> previously we were allowing (nearly) arbitrarily large arrays to be
> passed around.  The agreement as I understood it would be that the
> array itself would be sized up to a maximum of PAGE_SIZE, which means
> the number of entries cannot exceed PAGE_SIZE/sizeof(*user_pfn) (ie.
> 512 of x86).  I also suggested that we should have a #define for this so
> that vendor drivers can actually chunk their calls into allowable sizes
> if they need to and not need to guess the limit, ex.
> 
> include/linux/vfio.h
> #define VFIO_PAGE_PINNING_MAX_ENTRIES (PAGE_SIZE / sizeof(unsigned
> long))
> 
> If we wanted a simple limit to the number of entries per call, there
> would be no reason to have it based on PAGE_SIZE.  Thanks,
> 

Sorry I mis-interpreted it. Updating it on v13.
Thanks,
Kirti

> Alex
> 
>> +
>> +	group = vfio_group_get_from_dev(dev);
>> +	if (IS_ERR(group))
>> +		return PTR_ERR(group);
>> +
>> +	ret = vfio_group_add_container_user(group);
>> +	if (ret)
>> +		goto err_pin_pages;
>> +
>> +	container = group->container;
>> +	down_read(&container->group_lock);
>> +
>> +	driver = container->iommu_driver;
>> +	if (likely(driver && driver->ops->pin_pages))
>> +		ret = driver->ops->pin_pages(container->iommu_data, user_pfn,
>> +					     npage, prot, phys_pfn);
>> +	else
>> +		ret = -ENOTTY;
>> +
>> +	up_read(&container->group_lock);
>> +	vfio_group_try_dissolve_container(group);
>> +
>> +err_pin_pages:
>> +	vfio_group_put(group);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(vfio_pin_pages);
>> +
>> +/*
>> + * Unpin set of host PFNs for local domain only.
>> + * @dev [in] : device
>> + * @user_pfn [in]: array of user/guest PFNs to be unpinned. Number of user/guest
>> + *		  PFNs should not be greater than PAGE_SIZE.
>> + * @npage [in] :count of elements in array.  This count should not be greater
>> + *		than PAGE_SIZE.
>> + * Return error or number of pages unpinned.
>> + */
>> +int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
>> +{
>> +	struct vfio_container *container;
>> +	struct vfio_group *group;
>> +	struct vfio_iommu_driver *driver;
>> +	int ret;
>> +
>> +	if (!dev || !user_pfn || !npage)
>> +		return -EINVAL;
>> +
>> +	if (npage >= PAGE_SIZE)
>> +		return -E2BIG;
>> +
>> +	group = vfio_group_get_from_dev(dev);
>> +	if (IS_ERR(group))
>> +		return PTR_ERR(group);
>> +
>> +	ret = vfio_group_add_container_user(group);
>> +	if (ret)
>> +		goto err_unpin_pages;
>> +
>> +	container = group->container;
>> +	down_read(&container->group_lock);
>> +
>> +	driver = container->iommu_driver;
>> +	if (likely(driver && driver->ops->unpin_pages))
>> +		ret = driver->ops->unpin_pages(container->iommu_data, user_pfn,
>> +					       npage);
>> +	else
>> +		ret = -ENOTTY;
>> +
>> +	up_read(&container->group_lock);
>> +	vfio_group_try_dissolve_container(group);
>> +
>> +err_unpin_pages:
>> +	vfio_group_put(group);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(vfio_unpin_pages);
>> +
>>  /**
>>   * Module/class support
>>   */
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 2ba19424e4a1..9f3d58d3dfaf 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -259,8 +259,8 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
>>   * the iommu can only map chunks of consecutive pfns anyway, so get the
>>   * first page and all consecutive pages with the same locking.
>>   */
>> -static long vfio_pin_pages(unsigned long vaddr, long npage,
>> -			   int prot, unsigned long *pfn_base)
>> +static long vfio_pin_pages_remote(unsigned long vaddr, long npage,
>> +				  int prot, unsigned long *pfn_base)
>>  {
>>  	unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>>  	bool lock_cap = capable(CAP_IPC_LOCK);
>> @@ -318,8 +318,8 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
>>  	return i;
>>  }
>>  
>> -static long vfio_unpin_pages(unsigned long pfn, long npage,
>> -			     int prot, bool do_accounting)
>> +static long vfio_unpin_pages_remote(unsigned long pfn, long npage,
>> +				    int prot, bool do_accounting)
>>  {
>>  	unsigned long unlocked = 0;
>>  	long i;
>> @@ -382,9 +382,9 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
>>  		if (WARN_ON(!unmapped))
>>  			break;
>>  
>> -		unlocked += vfio_unpin_pages(phys >> PAGE_SHIFT,
>> -					     unmapped >> PAGE_SHIFT,
>> -					     dma->prot, false);
>> +		unlocked += vfio_unpin_pages_remote(phys >> PAGE_SHIFT,
>> +						    unmapped >> PAGE_SHIFT,
>> +						    dma->prot, false);
>>  		iova += unmapped;
>>  
>>  		cond_resched();
>> @@ -613,8 +613,8 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>>  
>>  	while (size) {
>>  		/* Pin a contiguous chunk of memory */
>> -		npage = vfio_pin_pages(vaddr + dma->size,
>> -				       size >> PAGE_SHIFT, prot, &pfn);
>> +		npage = vfio_pin_pages_remote(vaddr + dma->size,
>> +					      size >> PAGE_SHIFT, prot, &pfn);
>>  		if (npage <= 0) {
>>  			WARN_ON(!npage);
>>  			ret = (int)npage;
>> @@ -624,7 +624,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>>  		/* Map it! */
>>  		ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage, prot);
>>  		if (ret) {
>> -			vfio_unpin_pages(pfn, npage, prot, true);
>> +			vfio_unpin_pages_remote(pfn, npage, prot, true);
>>  			break;
>>  		}
>>  
>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index 0ecae0b1cd34..86f507d0f585 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -75,7 +75,11 @@ struct vfio_iommu_driver_ops {
>>  					struct iommu_group *group);
>>  	void		(*detach_group)(void *iommu_data,
>>  					struct iommu_group *group);
>> -
>> +	int		(*pin_pages)(void *iommu_data, unsigned long *user_pfn,
>> +				     int npage, int prot,
>> +				     unsigned long *phys_pfn);
>> +	int		(*unpin_pages)(void *iommu_data,
>> +				       unsigned long *user_pfn, int npage);
>>  };
>>  
>>  extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
>> @@ -127,6 +131,12 @@ static inline long vfio_spapr_iommu_eeh_ioctl(struct iommu_group *group,
>>  }
>>  #endif /* CONFIG_EEH */
>>  
>> +extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
>> +			  int npage, int prot, unsigned long *phys_pfn);
>> +
>> +extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
>> +			    int npage);
>> +
>>  /*
>>   * IRQfd - generic
>>   */
>