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: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 3a11132..1eacbb8 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -229,51 +229,6 @@ 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.
  */
 #define ccw_is_read(_ccw) (((_ccw)->cmd_code & 0x03) == 0x02)
@@ -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;