Commit c5e8083f authored by Eric Farman's avatar Eric Farman Committed by Heiko Carstens
Browse files

vfio/ccw: replace copy_from_iova with vfio_dma_rw 

It was suggested [1] that we replace the old copy_from_iova() routine
(which pins a page, does a memcpy, and unpins the page) with the
newer vfio_dma_rw() interface.

This has a modest improvement in the overall time spent through the
fsm_io_request() path, and simplifies some of the code to boot.

[1] https://lore.kernel.org/r/20220706170553.GK693670@nvidia.com/



Suggested-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: default avatarEric Farman <farman@linux.ibm.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarMatthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 254cb663

drivers/s390/cio/vfio_ccw_cp.c

+5 −51
Original line number Diff line number Diff line
@@ -228,51 +228,6 @@ static void convert_ccw0_to_ccw1(struct ccw1 *source, unsigned long len) 
	}

}



/*

 * Within the domain (@vdev), copy @n bytes from a guest physical

 * address (@iova) to a host physical address (@to).

 */

static long copy_from_iova(struct vfio_device *vdev, void *to, u64 iova,

			   unsigned long n)

{

	struct page_array pa = {0};

	int i, ret;

	unsigned long l, m;



	ret = page_array_alloc(&pa, iova, n);

	if (ret < 0)

		return ret;



	ret = page_array_pin(&pa, vdev);

	if (ret < 0) {

		page_array_unpin_free(&pa, vdev);

		return ret;

	}



	l = n;

	for (i = 0; i < pa.pa_nr; i++) {

		void *from = kmap_local_page(pa.pa_page[i]);



		m = PAGE_SIZE;

		if (i == 0) {

			from += iova & (PAGE_SIZE - 1);

			m -= iova & (PAGE_SIZE - 1);

		}



		m = min(l, m);

		memcpy(to + (n - l), from, m);

		kunmap_local(from);



		l -= m;

		if (l == 0)

			break;

	}



	page_array_unpin_free(&pa, vdev);



	return l;

}



/*

 * Helpers to operate ccwchain.

 */
@@ -471,10 +426,9 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp) 
	int len, ret;



	/* Copy 2K (the most we support today) of possible CCWs */

	len = copy_from_iova(vdev, cp->guest_cp, cda,

			     CCWCHAIN_LEN_MAX * sizeof(struct ccw1));

	if (len)

		return len;

	ret = vfio_dma_rw(vdev, cda, cp->guest_cp, CCWCHAIN_LEN_MAX * sizeof(struct ccw1), false);

	if (ret)

		return ret;



	/* Convert any Format-0 CCWs to Format-1 */

	if (!cp->orb.cmd.fmt)
@@ -572,7 +526,7 @@ static int ccwchain_fetch_direct(struct ccwchain *chain, 
	if (ccw_is_idal(ccw)) {

		/* Read first IDAW to see if it's 4K-aligned or not. */

		/* All subsequent IDAws will be 4K-aligned. */

		ret = copy_from_iova(vdev, &iova, ccw->cda, sizeof(iova));

		ret = vfio_dma_rw(vdev, ccw->cda, &iova, sizeof(iova), false);

		if (ret)

			return ret;

	} else {
@@ -601,7 +555,7 @@ static int ccwchain_fetch_direct(struct ccwchain *chain, 


	if (ccw_is_idal(ccw)) {

		/* Copy guest IDAL into host IDAL */

		ret = copy_from_iova(vdev, idaws, ccw->cda, idal_len);

		ret = vfio_dma_rw(vdev, ccw->cda, idaws, idal_len, false);

		if (ret)

			goto out_unpin;