From cdd346371e09709be8e46398bb097dc690a746f2 Mon Sep 17 00:00:00 2001 From: Dan Aloni Date: Sun, 28 May 2017 16:06:49 +0300 Subject: [PATCH] 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 CC: Alex Friedman CC: Keith Busch CC: Stefan Hajnoczi Reviewed-by: Keith Busch Signed-off-by: Stefan Hajnoczi --- 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;