[RFC PATCH v1 3/5] vfio-ccw: Copy CCW data outside length calculation

Eric Farman
2019-06-18T20:24:01Z

It doesn't make much sense to "hide" the copy to the channel_program
struct inside a routine that calculates the length of the chain.

Let's move it to the calling routine, which will later copy from
channel_program to the memory it allocated itself.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 37d513e86530..a55f8d110920 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -381,18 +381,8 @@ static void ccwchain_cda_free(struct ccwchain *chain, int idx)
static int ccwchain_calc_length(u64 iova, struct channel_program *cp)
{
struct ccw1 *ccw = cp->guest_cp;
- int cnt;
+ int cnt = 0;

- /*
- * Copy current chain from guest to host kernel.
- * Currently the chain length is limited to CCWCHAIN_LEN_MAX (256).
- * So copying 2K is enough (safe).
- */
- cnt = copy_ccw_from_iova(cp, ccw, iova, CCWCHAIN_LEN_MAX);
- if (cnt)
- return cnt;
-
- cnt = 0;
do {
cnt++;

@@ -446,7 +436,12 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
struct ccwchain *chain;
int len;

- /* Copy the chain from cda to cp, and count the CCWs in it */
+ /* Copy 2K (the most we support today) of possible CCWs */
+ len = copy_ccw_from_iova(cp, cp->guest_cp, cda, CCWCHAIN_LEN_MAX);
+ if (len)
+ return len;
+
+ /* Count the CCWs in the current chain */
len = ccwchain_calc_length(cda, cp);
if (len < 0)
return len;
--
2.17.1