linux-kernel - Re: [EXT] Re: [PATCH] nvme: Add abrupt shutdown support

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Message-ID: <20210705130456.GA239714@dhcp-10-100-145-180.wdc.com>
Date:   Mon, 5 Jul 2021 06:04:56 -0700
From:   Keith Busch <kbusch@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     "Shivamurthy Shastri (sshivamurthy)" <sshivamurthy@...ron.com>,
        "axboe@...com" <axboe@...com>,
        "sagi@...mberg.me" <sagi@...mberg.me>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shiva.linuxworks@...il.com" <shiva.linuxworks@...il.com>
Subject: Re: [EXT] Re: [PATCH] nvme: Add abrupt shutdown support

On Mon, Jul 05, 2021 at 01:53:49PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 05, 2021 at 11:15:51AM +0000, Shivamurthy Shastri (sshivamurthy) wrote:
> > For systems with passive electronic components to handle power-loss/battery-removal,
> > CC.SHN=10b will help to achieve safer shutdown with relatively lower power back-up 
> > requirements (at lower cost).
> > 
> > The module parameter gives flexibility to the host to decide shutdown type even during
> > boot failure. 
> 
> If you have a device that always prefers an abrupt please introduce a TP
> in the NVMe technical working group so that the hosts automatically
> do the right thing.  Requiring sysadmin intervention using a global
> kernel parameter is not the way to do this.

Is it the device that wants an abrupt shutdown or the platform? If the
platform's power is running on limited back-up supply, and could inform
the kernel's power management subsystem of this, then a driver could use
that to determine if the quick shutdown is appropriate.