Commit cfedb3d5 authored by Nicolin Chen's avatar Nicolin Chen Committed by Alex Williamson
Browse files

vfio/ccw: Only pass in contiguous pages 



This driver is the only caller of vfio_pin/unpin_pages that might pass
in a non-contiguous PFN list, but in many cases it has a contiguous PFN
list to process. So letting VFIO API handle a non-contiguous PFN list
is actually counterproductive.

Add a pair of simple loops to pass in contiguous PFNs only, to have an
efficient implementation in VFIO.

Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarEric Farman <farman@linux.ibm.com>
Tested-by: default avatarEric Farman <farman@linux.ibm.com>
Signed-off-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/20220723020256.30081-5-nicolinc@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 10e19d49

drivers/s390/cio/vfio_ccw_cp.c

+56 −14
Original line number Diff line number Diff line
@@ -90,6 +90,38 @@ static int pfn_array_alloc(struct pfn_array *pa, u64 iova, unsigned int len) 
	return 0;

}



/*

 * pfn_array_unpin() - Unpin user pages in memory

 * @pa: pfn_array on which to perform the operation

 * @vdev: the vfio device to perform the operation

 * @pa_nr: number of user pages to unpin

 *

 * Only unpin if any pages were pinned to begin with, i.e. pa_nr > 0,

 * otherwise only clear pa->pa_nr

 */

static void pfn_array_unpin(struct pfn_array *pa,

			    struct vfio_device *vdev, int pa_nr)

{

	int unpinned = 0, npage = 1;



	while (unpinned < pa_nr) {

		unsigned long *first = &pa->pa_iova_pfn[unpinned];

		unsigned long *last = &first[npage];



		if (unpinned + npage < pa_nr &&

		    *first + npage == *last) {

			npage++;

			continue;

		}



		vfio_unpin_pages(vdev, first, npage);

		unpinned += npage;

		npage = 1;

	}



	pa->pa_nr = 0;

}



/*

 * pfn_array_pin() - Pin user pages in memory

 * @pa: pfn_array on which to perform the operation
@@ -101,34 +133,44 @@ static int pfn_array_alloc(struct pfn_array *pa, u64 iova, unsigned int len) 
 */

static int pfn_array_pin(struct pfn_array *pa, struct vfio_device *vdev)

{

	int pinned = 0, npage = 1;

	int ret = 0;



	ret = vfio_pin_pages(vdev, pa->pa_iova_pfn, pa->pa_nr,

			     IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);

	while (pinned < pa->pa_nr) {

		unsigned long *first = &pa->pa_iova_pfn[pinned];

		unsigned long *last = &first[npage];



		if (pinned + npage < pa->pa_nr &&

		    *first + npage == *last) {

			npage++;

			continue;

		}



		ret = vfio_pin_pages(vdev, first, npage,

				     IOMMU_READ | IOMMU_WRITE,

				     &pa->pa_pfn[pinned]);

		if (ret < 0) {

			goto err_out;

	} else if (ret > 0 && ret != pa->pa_nr) {

		vfio_unpin_pages(vdev, pa->pa_iova_pfn, ret);

		} else if (ret > 0 && ret != npage) {

			pinned += ret;

			ret = -EINVAL;

			goto err_out;

		}

		pinned += npage;

		npage = 1;

	}



	return ret;



err_out:

	pa->pa_nr = 0;



	pfn_array_unpin(pa, vdev, pinned);

	return ret;

}



/* Unpin the pages before releasing the memory. */

static void pfn_array_unpin_free(struct pfn_array *pa, struct vfio_device *vdev)

{

	/* Only unpin if any pages were pinned to begin with */

	if (pa->pa_nr)

		vfio_unpin_pages(vdev, pa->pa_iova_pfn, pa->pa_nr);

	pa->pa_nr = 0;

	pfn_array_unpin(pa, vdev, pa->pa_nr);

	kfree(pa->pa_iova_pfn);

}