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dma/idxd: fix wrap-around in burst capacity calculation

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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: 9459de4edc ("dma/idxd: add burst capacity")
Cc: stable@dpdk.org

Reported-by: Sunil Pai G <sunil.pai.g@intel.com>
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Tested-by: Sunil Pai G <sunil.pai.g@intel.com>
Acked-by: Kevin Laatz <kevin.laatz@intel.com>
This commit is contained in:
Bruce Richardson 2022-01-11 13:41:04 +00:00 committed by Thomas Monjalon
parent 3277676319
commit 63990aeb08
1 changed files with 2 additions and 4 deletions
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6
drivers/dma/idxd/idxd_common.c
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@ -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));