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nvme: Fix get/set number of queues feature, again 

The number of queues that should be return by the admin command should:

  1) Only mention the number of non-admin queues.
  2) It is zero-based, meaning that '0 == one non-admin queue',
     '1 == two non-admin queues', and so forth.

Because our `num_queues` means the number of queues _plus_ the admin
queue, then the right calculation for the number returned from the admin
command is `num_queues - 2`, combining the two requirements mentioned.

The issue was discovered by reducing num_queues from 64 to 8 and running
a Linux VM with an SMP parameter larger than that (e.g. 22). It tries to
utilize all queues, and therefore fails with an invalid queue number
when trying to queue I/Os on the last queue.

Signed-off-by: Dan Aloni <dan@kernelim.com>
CC: Alex Friedman <alex@e8storage.com>
CC: Keith Busch <keith.busch@intel.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Dan Aloni 2017-05-28 16:06:49 +03:00 committed by Stefan Hajnoczi
parent 248b237356
commit cdd346371e
1 changed files with 2 additions and 2 deletions
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4
hw/block/nvme.c
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@ -615,7 +615,7 @@ static uint16_t nvme_get_feature(NvmeCtrl *n, NvmeCmd *cmd, NvmeRequest *req)
result = blk_enable_write_cache(n->conf.blk);
break;
case NVME_NUMBER_OF_QUEUES:
result = cpu_to_le32((n->num_queues - 1) | ((n->num_queues - 1) << 16));
result = cpu_to_le32((n->num_queues - 2) | ((n->num_queues - 2) << 16));
break;
default:
return NVME_INVALID_FIELD | NVME_DNR;
@ -636,7 +636,7 @@ static uint16_t nvme_set_feature(NvmeCtrl *n, NvmeCmd *cmd, NvmeRequest *req)
break;
case NVME_NUMBER_OF_QUEUES:
req->cqe.result =
cpu_to_le32((n->num_queues - 1) | ((n->num_queues - 1) << 16));
cpu_to_le32((n->num_queues - 2) | ((n->num_queues - 2) << 16));
break;
default:
return NVME_INVALID_FIELD | NVME_DNR;