From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pdx-out-012.esa.us-west-2.outbound.mail-perimeter.amazon.com (pdx-out-012.esa.us-west-2.outbound.mail-perimeter.amazon.com [35.162.73.231]) (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 72E6A4E4C55 for ; Mon, 28 Sep 2026 15:23:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=35.162.73.231 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790609012; cv=none; b=koqk1eotg3aTCK2wb1jDcIziM4qdSkMiSKLQR/l+eDXo/L1KjYITFhdD3U3Giqy+nmq5xmwofDUQ30JKx8z6Yuqt8ToeMrnydlQiq9506XzRBnfV7wUDsjh0AyEwBq6DSoGOmtXLUpXd8fsWvhg/QxXA83VE72SUlscP+Rqv9iE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790609012; c=relaxed/simple; bh=prL4mY5T7qdCLFQzKZtWBj5xenekzjprM/SYPDvtZrA=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=TvQqP47JnsvQwHPOVpAU3ip0gj4Ech4s88FpHQH+EIGwM/0rJlxYA2wll2GBoVTs5ypUmDwQ1Q7p2oCF0TugaJt/I51ZssT0aJg57/isGa1uA7YrK5DdtUixXz6yy73rqYhgW1EXdmd+L9//LaIfRc+CSNnGqhyoPw/dntHj12Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=N/7he2Fm; arc=none smtp.client-ip=35.162.73.231 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="N/7he2Fm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1790609010; x=1822145010; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ssc2XGYXxWt7KSvkGE64VLhm/JYqo0izQ0v9suh6vGk=; b=N/7he2Fm5SIlbha/tmYZs/oZHwH8l0eBQzIkeTzSQ3xdVb9x4qQi31I6 tNiJ6NiNNgK7LB24dfnzlLeeXIMG6WZ+3tbpbVfcewK5iUeb0gUse4Ob+ QWqvNSVILnzE4k9HY95x3B4UBM0YUKhOfPes5vdTBZ2sBEAa5E7kinMzw dkUFEwl9yx5VSaaxv/3Ex5l8EuvYHsUMVJjgiulLzwRZrLaD0QnROxSaL bUTBQPah1WNNHPb6CTfJsoFMXHhJL89yScViAfWMiYoEbRQ/GgWKtNBqu pjIlFh4gbA08s+Rv5gdqNeqs1OYDRjWTlJ4h1aV//FNjenk9ri34aQtP1 Q==; 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: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D031UWA001.ant.amazon.com (10.13.139.88) To EX19D001UWA001.ant.amazon.com (10.13.138.214) 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