[PATCH 2/2] vfio: ccw: validate the count field of a ccw before pinning

Dong Jia Shi
2017-10-11T02:38:22Z

If the count field of a ccw is zero, there is no need to
try to pin page(s) for it. Let's check the count value
before starting pinning operations.

Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 722f8b8c7273..d8f98ad9b029 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -105,7 +105,10 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
{
int ret = 0;

- if (!len || pa->pa_nr)
+ if (!len)
+ return 0;
+
+ if (pa->pa_nr)
return -EINVAL;

pa->pa_iova = iova;
@@ -501,6 +504,16 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,

ccw = chain->ch_ccw + idx;

+ if (!ccw->count) {
+ /*
+ * We just want the translation result of any direct ccw
+ * to be an IDA ccw, so let's add the IDA flag for it.
+ * Although the flag will be ignored by firmware.
+ */
+ ccw->flags |= CCW_FLAG_IDA;
+ return 0;
+ }
+
/*
* Pin data page(s) in memory.
* The number of pages actually is the count of the idaws which will be
@@ -541,6 +554,9 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,

ccw = chain->ch_ccw + idx;

+ if (!ccw->count)
+ return 0;
+
/* Calculate size of idaws. */
ret = copy_from_iova(cp->mdev, &idaw_iova, ccw->cda, sizeof(idaw_iova));
if (ret)
--
2.13.5