Hi Bruce,
> what values for the write_idx and ids_returned vars give this error, and how
> does masking help? I'd expect masking to increase the number of times the
> function returns zero, rather than decreasing it.
Here are the values from the idxd dump:
dev_capa: 0x500000051 - mem2mem sva handles_errors copy fill
max_vchans_supported: 1
nb_vchans_configured: 1
silent_mode: off
IDXD Private Data ==
Portal: 0x7ffff7ffb000
Config: { ring_size: 4096 }
Batch ring (sz = 129, max_batches = 128):
62370 62402 62434 62466 62498 62530 62562 62594 62626 62658 62690
62722 62754 62786 62818 62850 62882 62914 62946 62978 63010 63042
63074 6
3106 63138 63170 63202 63234 63266 63298 63330 63362 63394 63426
63458 63490 63522 63554 63586 63618 63650 63682 63714 63746 63778
63810 63842 63874 63906 63938 63970 64002 64034 64066 64098 6413
0 64162 64194 64226 64258 64290 64322 64354 64386 64418 64450 64482
64514 64546 64578 64610 64642 64674 64706 64738 64770 64802 64834
64866 64898 64930 64962 64994 65026 65058 65090 65122 65154
65186 65218 65250 65282 65314 65346 65378 65410 65442 65474 65506 [rd
ptr] 2 [wr ptr] 61442 61474 61506 61538 61570 61602 61634 61666 61698
61730 61762 61794 61826 61858 61890 61922 61954 61986 620
18 62050 62082 62114 62146 62178 62210 62242 62274 62306 62338
Curr batch: start = 2, size = 0
IDS: avail = 65506, returned: 65506
max packets per batch from hw: 1024
batches left: 127, ring space left: 4064
idxd->desc_ring_mask: 4095, used_space: 4128, used_space: 4128,
idxd->max_batch_size: 1024, idxd->batch_size: 0
write_idx: 4098, idxd->batch_idx_read: 98, idxd->batch_idx_write: 99,
idxd->desc_ring_mask - used_space: 65503
relevant data from above:
write_idx: 4098 , IDS returned: 65506, idxd->desc_ring_mask: 4095
without the fix :
used_space = write_idx - idxd->ids_returned; (4098 - 65506) = -61408
with fix:
used_space = (write_idx - idxd->ids_returned)& idxd->desc_ring_mask; (4098 -
65506)&4095 = 32
which seems to match the rd ptr and wr ptr.
Thanks and regards,
Sunil
