From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF69F3A451B for ; Fri, 8 May 2026 09:31:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778232713; cv=none; b=Qc6hzxtakRwCATdoKyBih6LetBHMNEkEHLd4lL+/oF2jsujiSGMjlFpWDZ6tvFu5IQWT5MzTZxDIS6U3QXeyrEyWwScmhxEYIOeD9y2VixlyPt+c0CxR/KBfCMu2nDdfNOpTXP3PL1hu1Pww274ESWcq57BPUcNXGp8oQAGHozA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778232713; c=relaxed/simple; bh=uA7GVZz2bi4jQUVlE6iItOdauDNxiqMvd6wJgnT5geE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kjJ4xTmU1VazGcuOxA8YRWj9Q9KMeFEQb+rWPnXit+MNpbfASZdZ12GcINNEA0jLwg3/fWyhlOZwxVcOYbMix+nFKrAj1suurHMNy4QdRXXkVB5IeGFsY4ouSMAQvpZ9ApR1F9/HJ5pT8e94cLomd0pnJguERg8/lo60LcxMr/E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ojFU2lve; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ojFU2lve" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51F41C2BCB0; Fri, 8 May 2026 09:31:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778232713; bh=uA7GVZz2bi4jQUVlE6iItOdauDNxiqMvd6wJgnT5geE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ojFU2lveFMGmHkHJ+rPBA4FXu291LnNpnuWu5MEr1SPktmx3lQRL4coRMuB1BB/+C DbiNLXK22WZhrBU0om+6vMaMRQ2x3mrvNgNgT/0LiM8ZdmgH3ZvivOB/vP1rCNd1bs zQoNA0ElyN1uUxqMDi8dvxyCuPoYo+v3i2zsySEgjVWKcrKpR6R0yXliIMZGBfXPvE e72APpNLjde0mEnXK1enikyWHJ6F23aQAukwOZfiVOAtVs7KE/+WOqgEXZTNZU737Z 32am9XBXsg4dU6ip0x9npqdaa6ejb107HGyjaJZd613yE/cxBKh2aU559wq5SE+9ck N1AyuCAPLbtfw== Date: Fri, 8 May 2026 10:31:48 +0100 From: Keith Busch To: Christoph Hellwig Cc: Maurizio Lombardi , Chao Shi , linux-nvme@lists.infradead.org, Sagi Grimberg , Jens Axboe , Tatsuya Sasaki , linux-kernel@vger.kernel.org, Sungwoo Kim , Dave Tian , Weidong Zhu Subject: Re: [PATCH] nvme: reserve a keep-alive admin tag for all transports Message-ID: References: <20260428022911.1288485-1-coshi036@gmail.com> <20260508090427.GA20593@lst.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260508090427.GA20593@lst.de> On Fri, May 08, 2026 at 11:04:27AM +0200, Christoph Hellwig wrote: > On Tue, Apr 28, 2026 at 08:24:35AM +0100, Keith Busch wrote: > > > This field specifies the timeout value for the Keep Alive feature in > > > milliseconds. [...] > > > The default value for this field is 0h for NVMe transports that do not require use of the Keep Alive > > > feature (e.g., NVMe over PCIe). For NVMe transports that require use of the Keep Alive feature > > > (e.g., RDMA and TCP), the default value for this field is 1D4C0h " > > > > > > To me, it sounds like for nvme-pci, keep alive isn't required, but could > > > be activated. > > > > The spec says the support is subject to the Transport binding > > specification, which does not exist in the PCIe transport spec. > > My memories from the fabrics working group back in the day is that we > explicitly intended to support it in PCIe. The wording in the spec > referring to transport specs I can find is: > > The NVMe Transport binding specification for the associated NVMe Transport > defines: > > o the minimum Keep Alive Timeout value, if any; > o the maximum Keep Alive Timeout value, if any; and > o if the Keep Alive Timer feature is required to be supported and enabled. > > which does not read to me like there is any required language in the > transport spec to require keep alive. So the absence of defining a minimum means it's simply optional? I suppose I can see it that way as the intended interpretation, but seems counter productive to do on PCIe when you can MMIO the controller status register to verify liveness. If the controller responds successfully to the feature, then I have to agree we need the host to do its part.