From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) (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 938B3A3B for ; Tue, 23 Aug 2022 07:06:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661238365; x=1692774365; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=2adFR0X7/dPlReestSB7DuXWGZcuS9kgjKJkDTUPHG4=; b=fayGn1qaWOG6GNzaVOIKVnWni6HvMaIvunhrdcm5IY1zzq1/DxZ8PRtp Nsl7jG0T9C+5L9L4hXk0JnNoAudKQRz2UiCaBvsMPYJTnAo0e+MZVkpgc 9+IbPx4zAvdB+VocRf9idY7jddbq8+Ozntd1cDbJXHLHvgCNthF8GLVaC J87ftMHrKvXgCMpO6beAtLhPIM43/yrc//7UEzRUUm+KnTUAxYjCSWgVK AXDoT1ASL7o1zQm6v0XQrEGVJvu0kcqrTH5SQ9hY5ZG9og3eWLhMlmlYI 8yJQY5P+7WdUjFecPYu3NpYxnD/W205OowpKANUQYQiOBDKX3dYz+qOAj g==; X-IronPort-AV: E=McAfee;i="6500,9779,10447"; a="292351807" X-IronPort-AV: E=Sophos;i="5.93,256,1654585200"; d="scan'208";a="292351807" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2022 00:06:01 -0700 X-IronPort-AV: E=Sophos;i="5.93,256,1654585200"; d="scan'208";a="642336552" Received: from xujinlon-mobl.ccr.corp.intel.com (HELO [10.254.211.102]) ([10.254.211.102]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Aug 2022 00:05:56 -0700 Message-ID: <35517add-de1c-f62a-aca2-8a627854e296@linux.intel.com> Date: Tue, 23 Aug 2022 15:05:53 +0800 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Cc: baolu.lu@linux.intel.com, Joerg Roedel , Jason Gunthorpe , Christoph Hellwig , Bjorn Helgaas , Kevin Tian , Ashok Raj , Will Deacon , Robin Murphy , Jean-Philippe Brucker , Dave Jiang , Vinod Koul , Eric Auger , Liu Yi L , Jacob jun Pan , Zhangfei Gao , Zhu Tony , iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 04/13] PCI: Allow PASID only when ACS enforced on upstreaming path Content-Language: en-US To: Bjorn Helgaas References: <20220818230020.GA2401272@bhelgaas> From: Baolu Lu In-Reply-To: <20220818230020.GA2401272@bhelgaas> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2022/8/19 07:00, Bjorn Helgaas wrote: > On Thu, Aug 18, 2022 at 07:53:15PM +0800, Baolu Lu wrote: >> On 2022/8/18 05:17, Bjorn Helgaas wrote: >>> On Wed, Aug 17, 2022 at 09:20:15AM +0800, Lu Baolu wrote: >>>> Some configurations of the PCI fabric will route device originated TLP >>>> packets based on the memory addresses. >>> This makes it sound like a few unusual configurations will route TLPs >>> based on memory addresses, but address routing is the default for all >>> PCIe Memory Requests, and ACS provides a way to override that default. >>> >>>> These configurations are incompatible with PASID as the PASID >>>> packets form a distinct address space. >>> I would say "the Requester ID/PASID combination forms a distinct >>> address space." >>> >>>> For instance, any configuration where switches are present >>>> without ACS enabled is incompatible. >>>> >>>> This enhances the pci_enable_pasid() interface by requiring the ACS to >>>> support Source Validation, Request Redirection, Completer Redirection, >>>> and Upstream Forwarding. This effectively means that devices cannot >>>> spoof their requester ID, requests and completions cannot be redirected, >>>> and all transactions are forwarded upstream, even as it passes through a >>>> bridge where the target device is downstream. >>> I think your patch actually requires all those features to be not just >>> "supported" but actually*enabled* for the entire path leading to the >>> device. >>> >>> To use the terms from the spec: >>> >>> "P2P Request Redirect" >>> "P2P Completion Redirect" >>> "Requester ID, Requests, and Completions" >>> >>> and maybe something like: >>> >>> ... even if the TLP looks like a P2P Request because its memory >>> address (ignoring the PASID) would fall in a bridge window and would >>> normally be routed downstream. >> Thank you for the suggestions. I will rephrase the commit message >> accordingly like this: >> >> >> PCI: Allow PASID only when ACS enforced on upstreaming path > PCI: Enable PASID only when ACS RR & UF enabled on upstream path > > The Requester ID/Process Address Space ID (PASID) combination > identifies an address space distinct from the PCI bus address space, > e.g., an address space defined by an IOMMU. > > But the PCIe fabric routes Memory Requests based on the TLP address, > ignoring any PASID (PCIe r6.0, sec 2.2.10.4), so a TLP with PASID that > *should* go upstream to the IOMMU may instead be routed as a P2P > Request if its address falls in a bridge window. > > To ensure that all Memory Requests with PASID are routed upstream, > only enable PASID if ACS P2P Request Redirect and Upstream Forwarding > are enabled for the path leading to the device. Yours is clear and straight-forward. I will update the patch with above. Thank you and very appreciated! Best regards, baolu