From: Dan Aloni <d...@kernelim.com>
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 <d...@kernelim.com>
CC: Alex Friedman <a...@e8storage.com>
CC: Keith Busch <keith.bu...@intel.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Keith Busch <keith.bu...@intel.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
hw/block/nvme.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 6071dc12d8..9aa32692a3 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -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;
--
2.13.5
