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

[Keith Busch]

On Fri, May 03, 2019 at 12:38:08PM +0900, Akinobu Mita wrote:
> 2019å5æ2æ(æ) 22:03 Keith Busch <keith.busch@xxxxxxxxx>:
> > 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.
> 
> OK.  I'll exclude the doorbell registers from register dump.  It will work
> out without the information if we have snapshot of the queues.

Could you actually explain how the rest is useful? I personally have
never encountered an issue where knowing these values would have helped:
every device timeout always needed device specific internal firmware
logs in my experience.