linux-kernel - [PATCH] nvme: Inform controller of doorbell config before unquiescing IO queues

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Message-ID: <20240110182855.1833512-1-wab@google.com>
Date: Wed, 10 Jan 2024 18:28:55 +0000
From: William Butler <wab@...gle.com>
To: Keith Busch <kbusch@...nel.org>, Pavel Emelyanov <xemul@...nvz.org>, Christoph Hellwig <hch@....de>, 
	Sagi Grimberg <sagi@...mberg.me>
Cc: Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org, 
	linux-nvme@...ts.infradead.org, William Butler <wab@...gle.com>
Subject: [PATCH] nvme: Inform controller of doorbell config before unquiescing
 IO queues

During resets, if queues are unquiesced first, then the host can submit
IOs to the controller using shadow doorbell logic but the controller
won't be aware. This can lead to necessary MMIO doorbells from being
not issued, causing requests to be delayed and timed-out.

Signed-off-by: William Butler <wab@...gle.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 61af7ff1a9d6..f87c51a946b3 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2743,10 +2743,10 @@ static void nvme_reset_work(struct work_struct *work)
 	 * controller around but remove all namespaces.
 	 */
 	if (dev->online_queues > 1) {
+		nvme_dbbuf_set(dev);
 		nvme_unquiesce_io_queues(&dev->ctrl);
 		nvme_wait_freeze(&dev->ctrl);
 		nvme_pci_update_nr_queues(dev);
-		nvme_dbbuf_set(dev);
 		nvme_unfreeze(&dev->ctrl);
 	} else {
 		dev_warn(dev->ctrl.device, "IO queues lost\n");
-- 
2.43.0.275.g3460e3d667-goog