From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C843BCA5FA2 for ; Mon, 28 Sep 2026 15:23:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ssc2XGYXxWt7KSvkGE64VLhm/JYqo0izQ0v9suh6vGk=; b=dyD5NqWEDy41PY6mH4EU4qbdCf QHQQKYIDVCLZQyl9WRGvO8XSByWwo10N81yaIuu+LnYPaUG6vsKMLRB90hwxZfQ/B/RAC8jTA4puc 6S3cgNBJX00y8JKrOfP6cl/F/Lf0W+DF9JZLGq99sn5aWQ5mA6Dqbu0TCN1CscCP3ZoSaHhst0icC ckgDfKjIES/SBdcs1hSfUYkalCW8F48i6TYf+F/KPiCeZW7GFVaITtJKSb7BQakac1TYklUPE7BdL aauT3vU/GVwF0aVt3Bf98ccvdSxFUPEhrIOXmnNsa0cp8zz4fuomc1D/yrVeQTK2QxSo0x5wHkO1v EOQ70V1A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBDCZ-00000000t2k-10ZK; Mon, 28 Sep 2026 15:23:35 +0000 Received: from pdx-out-012.esa.us-west-2.outbound.mail-perimeter.amazon.com ([35.162.73.231]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBDCW-00000000t25-3jEO for linux-arm-kernel@lists.infradead.org; Mon, 28 Sep 2026 15:23:34 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1790609012; x=1822145012; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ssc2XGYXxWt7KSvkGE64VLhm/JYqo0izQ0v9suh6vGk=; b=F2tkkRUuqkd1iY1RRCixXQWiBhVL7OgihXnZIF1RCKOWD1zIX3w2HlwP AEfZkvTXX0F3ubBpGv1Gur4A6oK2C7NQv/Qs+iyH5ooEcfJg1x8Gy1M24 EsTspvEJ/sSAhUwh82SjQme8lg+9nvXzv+vL8CBx3FxI3rcwywWZSR3qJ PH9WgGyOoJJybjKeVCQiZ7KKE3AhaPDUVIRRA+DKSGa/jYR1e7F43DN+F pHDfRB4z2DQCj3uh4RVM/n6G0ZNcxL0zK21N/OgkPmUMWt0FCBeQV6hDl Sn3IAA/gazxU7er7YSECJ8VDzk8jQBncmhnk43+tasic9syDFtNWfSB1G A==; X-CSE-ConnectionGUID: jnJ9/YN1TZSLsI2f6lzYSw== X-CSE-MsgGUID: 9bwnKBOuR0yNrVpk5p4H0w== X-IronPort-AV: E=Sophos;i="6.27,128,1787011200"; d="scan'208";a="29644157" Received: from ip-10-5-12-219.us-west-2.compute.internal (HELO smtpout.naws.us-west-2.prod.farcaster.email.amazon.dev) ([10.5.12.219]) by internal-pdx-out-012.esa.us-west-2.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2026 15:23:24 +0000 Received: from EX19MTAUWB002.ant.amazon.com [205.251.233.48:12407] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.13.104:2525] with esmtp (Farcaster) id ea5ba36c-33b9-4f1a-b9d1-70d08488d952; Mon, 28 Sep 2026 15:23:24 +0000 (UTC) X-Farcaster-Flow-ID: ea5ba36c-33b9-4f1a-b9d1-70d08488d952 Received: from EX19D001UWA001.ant.amazon.com (10.13.138.214) by EX19MTAUWB002.ant.amazon.com (10.250.64.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.49; Mon, 28 Sep 2026 15:23:23 +0000 Received: from 7cf34dda9133.amazon.com (10.106.178.42) by EX19D001UWA001.ant.amazon.com (10.13.138.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.49; Mon, 28 Sep 2026 15:23:21 +0000 From: Cristian Prundeanu To: CC: , , , , , , , , , , , , , Cristian Prundeanu Subject: Re: [PATCH v10 00/13] iommu/arm-smmu-v3: Adopt the crashed kernel's stream table for kdump Date: Mon, 28 Sep 2026 10:23:02 -0500 Message-ID: <20260928152302.58271-1-cpru@amazon.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.106.178.42] X-ClientProxiedBy: EX19D031UWA001.ant.amazon.com (10.13.139.88) To EX19D001UWA001.ant.amazon.com (10.13.138.214) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260928_082332_983431_23E2E71F X-CRM114-Status: GOOD ( 10.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sun, Aug 30, 2026 at 04:18:01PM -0700, Nicolin Chen wrote: > To safely absorb in-flight DMA, the kdump kernel must leave SMMUEN=1 intact > and avoid modifying STRTAB_BASE. This allows HW to continue translating in- > flight DMA using the crashed kernel's page tables until the endpoint device > drivers probe and quiesce their respective hardware. Tested v10 on AWS Graviton4 bare metal (m8g.metal-24xl: Neoverse V2, single SMMUv3 with a 2-level stream table). On this platform, if the SMMU aborts a NIC DMA read, firmware resets the host. An unpatched kernel fails kdump when the NIC is still fetching from memory as the SMMU probe installs a fresh stream table. Reproducer: sysrq-c while the NIC receives ~100 kpps of UDP over 64 flows, spread across most RX queues. The kdump initramfs omits the NIC driver, so nothing quiesces the device. Results using Amazon Linux 2023 with kdump kernel 6.18.39: - Unpatched: 2/2 failures. The SMMU logs read and write translation aborts ~2.5 s after the panic, and the host resets before the vmcore is written. - v7.3-rc1 + this series: 3/3 complete vmcores, no translation aborts. The kdump kernel logs "kdump: adopting crashed kernel's stream table" and "kdump: retaining SMMUEN for in-flight DMA". In one run the NIC driver was present, so the device was also re-probed and reset. Tested-by: Cristian Prundeanu