linux-kernel - Re: [PATCH v2 08/14] nvme: Implement cross-controller reset recovery

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Message-ID: <20260210222732.GQ3729-mkhalfella@purestorage.com>
Date: Tue, 10 Feb 2026 14:27:32 -0800
From: Mohamed Khalfella <mkhalfella@...estorage.com>
To: James Smart <jsmart833426@...il.com>
Cc: Justin Tee <justin.tee@...adcom.com>,
	Naresh Gottumukkala <nareshgottumukkala83@...il.com>,
	Paul Ely <paul.ely@...adcom.com>,
	Chaitanya Kulkarni <kch@...dia.com>, Christoph Hellwig <hch@....de>,
	Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
	Sagi Grimberg <sagi@...mberg.me>,
	Aaron Dailey <adailey@...estorage.com>,
	Randy Jennings <randyj@...estorage.com>,
	Dhaval Giani <dgiani@...estorage.com>,
	Hannes Reinecke <hare@...e.de>, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 08/14] nvme: Implement cross-controller reset recovery

On Tue 2026-02-10 14:09:27 -0800, James Smart wrote:
> On 1/30/2026 2:34 PM, Mohamed Khalfella wrote:
> ...
> > +unsigned long nvme_fence_ctrl(struct nvme_ctrl *ictrl)
> > +{
> > +	unsigned long deadline, now, timeout;
> > +	struct nvme_ctrl *sctrl;
> > +	u32 min_cntlid = 0;
> > +	int ret;
> > +
> > +	timeout = nvme_fence_timeout_ms(ictrl);
> > +	dev_info(ictrl->device, "attempting CCR, timeout %lums\n", timeout);
> > +
> > +	now = jiffies;
> > +	deadline = now + msecs_to_jiffies(timeout);
> > +	while (time_before(now, deadline)) {
> 
> Q: don't we have something to identify the controller's subsystem 
> supports CCR before we starting selecting controllers and sending CCR ?
> 
> I would think on older devices that don't support it we should be 
> skipping this loop.   The loop could delay the Time-Based delay without 
> any CCR.

I do not think we have something that identifies CCR support at
subsystem level. The spec defines CCRL at the controller level. The loop
should not that bad. nvme_find_ctrl_ccr() should return NULL if CCR is
not supported and nvme_fence_ctrl() will return immediately.

> 
> -- james
>