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[202.3.121.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7722a26a4e5sm13363163b3a.19.2025.09.02.03.35.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 03:35:23 -0700 (PDT) Message-ID: <2841bd1b7910bd0e1b263b393152f2cb13dd3ae3.camel@gmail.com> Subject: Re: [PATCH] nvme: Use non zero KATO for persistent discovery connections From: Martin George To: alistair23@gmail.com, kbusch@kernel.org, axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, linux-nvme@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Alistair Francis Date: Tue, 02 Sep 2025 16:05:19 +0530 In-Reply-To: <20250902035211.2953174-1-alistair.francis@wdc.com> References: <20250902035211.2953174-1-alistair.francis@wdc.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-09-02 at 13:52 +1000, alistair23@gmail.com wrote: > From: Alistair Francis >=20 > The NVMe Base Specification 2.1 states that: >=20 > """ > A host requests an explicit persistent connection ... by specifying a > non-zero Keep Alive Timer value in the Connect command. > """ >=20 > As such if we are starting a persistent connection to a discovery > controller and the KATO is currently 0 we need to update KATO to a > non > zero value to avoid continuous timeouts on the target. >=20 >=20 When would this ever happen? Won't nvme-cli & nvme/host/fabrics.c in the kernel ensure a PDC (persistent discovery controller) would always have the KATO either default set to NVMF_DEF_DISC_TMO (i.e. 30s) or any positive int value & not zero? Do you have a test log for the above scenario where the KATO ends up being zero for a PDC? -Martin