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Date:   Fri, 26 Aug 2022 11:26:26 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>,
        Christoph Hellwig <hch@infradead.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Vinod Koul <vkoul@kernel.org>,
        Eric Auger <eric.auger@redhat.com>,
        Liu Yi L <yi.l.liu@intel.com>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Zhangfei Gao <zhangfei.gao@linaro.org>,
        Zhu Tony <tony.zhu@intel.com>, iommu@lists.linux.dev,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v12 04/17] PCI: Enable PASID only when ACS RR & UF
 enabled on upstream path
Message-ID: <YwjYEpydbJ8z0Kmf@nvidia.com>
References: <20220826121141.50743-1-baolu.lu@linux.intel.com>
 <20220826121141.50743-5-baolu.lu@linux.intel.com>
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On Fri, Aug 26, 2022 at 08:11:28PM +0800, Lu Baolu wrote:
> 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.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Suggested-by: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> Tested-by: Tony Zhu <tony.zhu@intel.com>
> ---
>  drivers/pci/ats.c | 3 +++
>  1 file changed, 3 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason