[PATCH v3 0/1] nvme: Fix problem when booting from NVMe drive was leading to a hang.

[Michael Kropaczek <michael.kropaczek@solidigm.com>]

Description:

During endurance test, when a system was rebooted from NVMe drive, boot
process hung occasionally. The number of reboot cycles was set to 1000,
with interval of 120s. Hang occurred after ~300 reboot cycles.
After investigating the cause, it was established that NVMe driver
did not disable host memory during shutdown leaving NVMe controller
in a state preventing proper initialization in BIOS pre-boot stage.
Adding of the call to nvme_set_host_mem(dev, 0), when in shutdown,
fixed the issue.
In this version redundant comments were removed.

Michael Kropaczek (1):
  nvme: Fix problem when booting from NVMe drive was leading to a hang.

 drivers/nvme/host/pci.c | 3 +++
 1 file changed, 3 insertions(+)


base-commit: 8d30528a170905ede9ab6ab81f229e441808590b
-- 
2.34.1

From 054a4e846d967b0b37d0f398166c1f56ef536a72 Mon Sep 17 00:00:00 2001
From: Michael Kropaczek <michael.kropaczek@solidigm.com>
Date: Thu, 7 Mar 2024 14:51:30 -0800
Subject: [PATCH v3 1/1] nvme: Fix problem when booting from NVMe drive was
 leading to a hang.
To: linux-nvme@lists.infradead.org
Cc: Keith Busch <kbusch@kernel.org>,
    Jens Axboe <axboe@fb.com>,
    Christoph Hellwig <hch@lst.de>,
    Sagi Grimberg <sagi@grimberg.me>,
    Michael Kropaczek <michael.kropaczek@solidigm.com>

On certain host architectures/HW, DRAM was keeping memory contents over reboot
cycles. Certain NVMe controllers were accessing host memory after startup which
led to undefined state, preventing proper initialization in BIOS boot stage.
Freeing host memory during host's shutdown prevents the problem from occurring.

Signed-off-by: Michael Kropaczek <michael.kropaczek@solidigm.com>
---
 drivers/nvme/host/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index e6267a6aa380..bda7cf5ff674 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2593,6 +2593,9 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
 			nvme_wait_freeze_timeout(&dev->ctrl, NVME_IO_TIMEOUT);
 	}
 
+	if (shutdown && dev->hmb)
+		nvme_set_host_mem(dev, 0);
+
 	nvme_quiesce_io_queues(&dev->ctrl);
 
 	if (!dead && dev->ctrl.queue_count > 0) {
-- 
2.34.1