| Message ID | 20171011023822.42948-3-bjsdjshi@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 11 Oct 2017 04:38:22 +0200 Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote: > 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(-) This sounds reasonable, and I could not spot anything in the architecture that speaks against simply setting the IDA flag. Hopefully there's nothing buried out of sight :)
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)