On 5/6/19 11:37 AM, Cornelia Huck wrote:
On Fri, 3 May 2019 15:49:12 +0200
Eric Farman <farman@xxxxxxxxxxxxx> wrote:
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" (an invented
definition to simply mean it ends in a zero),
The "Common I/O Device Commands" document actually defines this :)
Blech, okay so I didn't look early enough in that document. Section 1.5
it is. :)
let's permit that to go
through to the hardware. There's nothing inherently unique about
those command codes versus one that ends in an eight [1], or any other
otherwise valid command codes that are undefined for the device type
in question.
But I agree that everything possible should be sent 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@xxxxxxxxxxxxx>
---
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 36d76b821209..c0a52025bf06 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -289,8 +289,6 @@ 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)
@@ -314,6 +312,10 @@ 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;
+
Don't you need to return 0 here for any test command as well?
(If I read the doc correctly, we'll just get a unit check in any case,
as there are no parallel I/O interfaces on modern s390 boxes. Even if
we had a parallel I/O interface, we'd just collect the status, and not
get any data transfer. FWIW, the QEMU ccw interpreter for emulated
devices rejects test ccws with a channel program check, which looks
wrong; should be a command reject instead.)
I will go back and look. I thought when I sent a test command with an
address that wasn't translated I got an unhappy result, which is why I
ripped this check out.
I was trying to use test CCWs as a safety valve for Halil's Status
Modifier concern, so maybe I had something else wrong on that pile.
(The careful observer would note that that code was not included here. :)
/* If the skip flag is off, then data will be transferred */
if (!ccw_is_skip(ccw))
return 1;
@@ -398,7 +400,7 @@ 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);
@@ -723,9 +725,6 @@ 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);
