[RFC PATCH v1 2/5] vfio-ccw: Skip second copy of guest cp to host

Eric Farman
2019-06-18T20:24:02Z

We already pinned/copied/unpinned 2K (256 CCWs) of guest memory
to the host space anchored off vfio_ccw_private. There's no need
to do that again once we have the length calculated, when we could
just copy the section we need to the "permanent" space for the I/O.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index f358502376be..37d513e86530 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -444,7 +444,7 @@ static int ccwchain_loop_tic(struct ccwchain *chain,
static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
{
struct ccwchain *chain;
- int len, ret;
+ int len;

/* Copy the chain from cda to cp, and count the CCWs in it */
len = ccwchain_calc_length(cda, cp);
@@ -457,12 +457,8 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
return -ENOMEM;
chain->ch_iova = cda;

- /* Copy the new chain from user. */
- ret = copy_ccw_from_iova(cp, chain->ch_ccw, cda, len);
- if (ret) {
- ccwchain_free(chain);
- return ret;
- }
+ /* Copy the actual CCWs into the new chain */
+ memcpy(chain->ch_ccw, cp->guest_cp, len * sizeof(struct ccw1));

/* Loop for tics on this new chain. */
return ccwchain_loop_tic(chain, cp);
--
2.17.1