Re: [PATCH 0/4] nvme-pci: support device coredump

[Keith Busch]

On Thu, May 02, 2019 at 05:59:17PM +0900, Akinobu Mita wrote:
> This enables to capture snapshot of controller information via device
> coredump machanism, and it helps diagnose and debug issues.
> 
> The nvme device coredump is triggered before resetting the controller
> caused by I/O timeout, and creates the following coredump files.
> 
> - regs: NVMe controller registers, including each I/O queue doorbell
>         registers, in nvme-show-regs style text format.

You're supposed to treat queue doorbells as write-only. Spec says:

  The host should not read the doorbell registers. If a doorbell register
  is read, the value returned is vendor specific.