Re: [PATCH] nvme-pci: skip FLR after a failed controller reset

[sashiko-bot@kernel.org]

> nvme_disable_ctrl() already waits up to CAP.TO for CSTS.RDY to clear.
> If that times out, nvme_pci_configure_admin_queue() currently issues a
> PCIe Function Level Reset and retries.
> 
> FLR is performed with PCI config cycles. Those cycles take
> pci_config_lock, a raw spinlock, and wait for the endpoint to complete
> the transaction. A wedged NVMe function can stall that completion.
> Other CPUs then spin in pci_conf1_read() -- including ACPI PCI config
> from an unrelated device -- and the NMI watchdog reports a hard lockup.
> 
> This was observed on an x86_64 UGREEN DXP4800 (kernel 6.18.15) with two
> ZHITAI Ti600 NVMe devices used as bcache. Each disk independently:
> 
>   nvme: I/O timeout, reset controller
>   nvme: Device not ready; aborting reset, CSTS=0x1
> [ ... ]
> Cc: Keith Busch <kbusch@kernel.org>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Signed-off-by: Haowen Bai <calvin.bai@ugreen.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260921140732.2942207-1-calvin.bai@ugreen.com?part=1