The burst capacity calculation code assumes that the write and read
(i.e. ids_returned) values both wrap at the ring-size, but the read
value instead wraps as UINT16_MAX. Therefore, instead of just adding
ring-size to the write value in case the read is greater, we need to
just always mask the result to ensure a correct, in-range, value.
Fixes: 9459de4edc99 ("dma/idxd: add burst capacity")
Cc: kevin.la...@intel.com
Cc: sta...@dpdk.org
Reported-by: Sunil Pai G <sunil.pa...@intel.com>
Signed-off-by: Bruce Richardson <bruce.richard...@intel.com>
---
drivers/dma/idxd/idxd_common.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/dma/idxd/idxd_common.c b/drivers/dma/idxd/idxd_common.c
index 4442d1cbbd..ea6413cc7a 100644
--- a/drivers/dma/idxd/idxd_common.c
+++ b/drivers/dma/idxd/idxd_common.c
@@ -480,10 +480,8 @@ idxd_burst_capacity(const void *dev_private, uint16_t
vchan __rte_unused)
idxd->batch_idx_write + 1 == idxd->batch_idx_read)
return 0;
- /* For descriptors, check for wrap-around on write but not read */
- if (idxd->ids_returned > write_idx)
- write_idx += idxd->desc_ring_mask + 1;
- used_space = write_idx - idxd->ids_returned;
+ /* Subtract and mask to get in correct range */
+ used_space = (write_idx - idxd->ids_returned) & idxd->desc_ring_mask;
const int ret = RTE_MIN((idxd->desc_ring_mask - used_space),
(idxd->max_batch_size - idxd->batch_size));
--
2.32.0
