[PATCH v3 3/3] s390/cio: Remove vfio-ccw checks of command codes

Eric Farman
2019-05-16T16:14:14Z

If the CCW being processed is a No-Operation, then by definition no
data is being transferred. Let's fold those checks into the normal
CCW processors, rather than skipping out early.

Likewise, if the CCW being processed is a "test" (a category defined
here as an opcode that contains zero in the lowest four bits) then no
special processing is necessary as far as vfio-ccw is concerned.
These command codes have not been valid since the S/370 days, meaning
they are invalid in the same way as one that ends in an eight [1] or
an otherwise valid command code that is undefined for the device type
in question. Considering that, let's just process "test" CCWs like
any other CCW, and send everything to the hardware.

[1] POPS states that a x08 is a TIC CCW, and that having any high-order
bits enabled is invalid for format-1 CCWs. For format-0 CCWs, the
high-order bits are ignored.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index c77c9b4cd2a8..f73cfcfdd032 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -295,8 +295,6 @@ static long copy_ccw_from_iova(struct channel_program *cp,
#define ccw_is_read_backward(_ccw) (((_ccw)->cmd_code & 0x0F) == 0x0C)
#define ccw_is_sense(_ccw) (((_ccw)->cmd_code & 0x0F) == CCW_CMD_BASIC_SENSE)

-#define ccw_is_test(_ccw) (((_ccw)->cmd_code & 0x0F) == 0)
-
#define ccw_is_noop(_ccw) ((_ccw)->cmd_code == CCW_CMD_NOOP)

#define ccw_is_tic(_ccw) ((_ccw)->cmd_code == CCW_CMD_TIC)
@@ -320,6 +318,10 @@ static inline int ccw_does_data_transfer(struct ccw1 *ccw)
if (ccw->count == 0)
return 0;

+ /* If the command is a NOP, then no data will be transferred */
+ if (ccw_is_noop(ccw))
+ return 0;
+
/* If the skip flag is off, then data will be transferred */
if (!ccw_is_skip(ccw))
return 1;
@@ -404,7 +406,7 @@ static void ccwchain_cda_free(struct ccwchain *chain, int idx)
{
struct ccw1 *ccw = chain->ch_ccw + idx;

- if (ccw_is_test(ccw) || ccw_is_noop(ccw) || ccw_is_tic(ccw))
+ if (ccw_is_tic(ccw))
return;

kfree((void *)(u64)ccw->cda);
@@ -730,9 +732,6 @@ static int ccwchain_fetch_one(struct ccwchain *chain,
{
struct ccw1 *ccw = chain->ch_ccw + idx;

- if (ccw_is_test(ccw) || ccw_is_noop(ccw))
- return 0;
-
if (ccw_is_tic(ccw))
return ccwchain_fetch_tic(chain, idx, cp);

--
2.17.1