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Wed, 22 Jan 2025 10:21:01 +0000 Received: from EX19MTAUWB002.ant.amazon.com (10.250.64.231) by EX19D009UWB001.ant.amazon.com (10.13.138.58) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.39; Wed, 22 Jan 2025 10:21:00 +0000 Received: from email-imr-corp-prod-iad-all-1b-a03c1db8.us-east-1.amazon.com (10.25.36.214) by mail-relay.amazon.com (10.250.64.228) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.39 via Frontend Transport; Wed, 22 Jan 2025 10:21:00 +0000 Received: from HFA15-G9FV5D3.amazon.com (unknown [10.85.143.175]) by email-imr-corp-prod-iad-all-1b-a03c1db8.us-east-1.amazon.com (Postfix) with ESMTP id 98C4080305; Wed, 22 Jan 2025 10:20:55 +0000 (UTC) From: David Arinzon To: David Miller , Jakub Kicinski , CC: David Arinzon , Eric Dumazet , Paolo Abeni , Richard Cochran , "Woodhouse, David" , "Machulsky, Zorik" , "Matushevsky, Alexander" , Saeed Bshara , "Wilson, Matt" , "Liguori, Anthony" , "Bshara, Nafea" , "Schmeilin, Evgeny" , "Belgazal, Netanel" , "Saidi, Ali" , "Herrenschmidt, Benjamin" , "Kiyanovski, Arthur" , "Dagan, Noam" , "Bernstein, Amit" , "Agroskin, Shay" , "Abboud, Osama" , "Ostrovsky, Evgeny" , "Tabachnik, Ofir" , "Machnikowski, Maciek" , "Rahul Rameshbabu" , Gal Pressman Subject: [PATCH v5 net-next 2/5] net: ena: PHC silent reset Date: Wed, 22 Jan 2025 12:20:37 +0200 Message-ID: <20250122102040.752-3-darinzon@amazon.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250122102040.752-1-darinzon@amazon.com> References: <20250122102040.752-1-darinzon@amazon.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org Each PHC device kernel registration receives a unique kernel index, which is associated with a new PHC device file located at "/dev/ptp". This device file serves as an interface for obtaining PHC timestamps. Examples of tools that use "/dev/ptp" include testptp [1] and chrony [2]. A reset flow may occur in the ENA driver while PHC is active. During a reset, the driver will unregister and then re-register the PHC device with the kernel. Under race conditions, particularly during heavy PHC loads, the driver’s reset flow might complete faster than the kernel’s PHC unregister/register process. This can result in the PHC index being different from what it was prior to the reset, as the PHC index is selected using kernel ID allocation [3]. While driver rmmod/insmod are done by the user, a reset may occur at anytime, without the user awareness, consequently, the driver might receive a new PHC index after the reset, potentially compromising the user experience. To prevent this issue, the PHC flow will detect the reset during PHC destruction and will skip the PHC unregister/register calls to preserve the kernel PHC index. During the reset flow, any attempt to get a PHC timestamp will fail as expected, but the kernel PHC index will remain unchanged. [1]: https://github.com/torvalds/linux/blob/v6.1/tools/testing/selftests/ptp/testptp.c [2]: https://github.com/mlichvar/chrony [3]: https://www.kernel.org/doc/html/latest/core-api/idr.html Signed-off-by: Amit Bernstein Signed-off-by: David Arinzon --- drivers/net/ethernet/amazon/ena/ena_phc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/amazon/ena/ena_phc.c b/drivers/net/ethernet/amazon/ena/ena_phc.c index 87495de0..5c1acd88 100644 --- a/drivers/net/ethernet/amazon/ena/ena_phc.c +++ b/drivers/net/ethernet/amazon/ena/ena_phc.c @@ -107,6 +107,10 @@ static int ena_phc_register(struct ena_adapter *adapter) phc_info = adapter->phc_info; clock_info = &phc_info->clock_info; + /* PHC may already be registered in case of a reset */ + if (ena_phc_is_active(adapter)) + return 0; + phc_info->adapter = adapter; spin_lock_init(&phc_info->lock); @@ -133,7 +137,11 @@ static void ena_phc_unregister(struct ena_adapter *adapter) { struct ena_phc_info *phc_info = adapter->phc_info; - if (ena_phc_is_active(adapter)) { + /* During reset flow, PHC must stay registered + * to keep kernel's PHC index + */ + if (ena_phc_is_active(adapter) && + !test_bit(ENA_FLAG_TRIGGER_RESET, &adapter->flags)) { ptp_clock_unregister(phc_info->clock); phc_info->clock = NULL; }