[SEABIOS] [PATCH 1/1] nvme: fix I/O queue length calculation overflow

[Matt DeVillier]

> From a17975b5fe0cb2b17fdf0335430d5f4d2ab3ba4d Mon Sep 17 00:00:00 2001

From: Matt DeVillier 
Date: Sun, 12 Aug 2018 15:26:59 -0500
Subject: [PATCH 1/1] nvme: fix I/O queue length calculation overflow

Commit cd47172 changed the I/O queue length calculation to use the
Maximum Queue Entries Supported (MQES) value from the capabilities
register, plus one, with a maximum value of NVME_PAGE_SIZE.

An unintended effect from this is that a MQES value of 0xFFFF yields
a length of zero, resulting in the queue allocation failing. Fix this
by checking for a zero length when checking that the length exceeds
NVME_PAGE_SIZE, and setting to NVME_PAGE_SIZE.

TEST: build/boot on a Purism Librem13v2 with a MyDigitalSSD BPX NVMe
drive, which reports a MQES of 0xFFFF. Verify NVMe drive present in
boot menu and OS boots successfully.

Signed-off-by: Matt DeVillier 
---
 src/hw/nvme.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/hw/nvme.c b/src/hw/nvme.c
index e6d739d..c2d6863 100644
--- a/src/hw/nvme.c
+++ b/src/hw/nvme.c
@@ -319,7 +319,7 @@ nvme_create_io_cq(struct nvme_ctrl *ctrl, struct
nvme_cq *cq, u16 q_idx)
     int rc;
     struct nvme_sqe *cmd_create_cq;
     u16 length = 1 + (ctrl->reg->cap & 0xffff);
-    if (length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
+    if (length == 0 || length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
         length = NVME_PAGE_SIZE / sizeof(struct nvme_cqe);

rc = nvme_init_cq(ctrl, cq, q_idx, length);
@@ -363,7 +363,7 @@ nvme_create_io_sq(struct nvme_ctrl *ctrl, struct
nvme_sq *sq, u16 q_idx, struct
     int rc;
     struct nvme_sqe *cmd_create_sq;
     u16 length = 1 + (ctrl->reg->cap & 0xffff);
-    if (length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
+    if (length == 0 || length > NVME_PAGE_SIZE / sizeof(struct nvme_cqe))
         length = NVME_PAGE_SIZE / sizeof(struct nvme_cqe);

rc = nvme_init_sq(ctrl, sq, q_idx, length, cq);