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Date:   Wed, 29 Mar 2023 13:50:02 +0530
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Subject: Re: [PATCH v2 4/8] iommu/vt-d: Reserve RID_PASID from global SVA
 PASID space
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To:     Baolu Lu <baolu.lu@linux.intel.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>, iommu@lists.linux.dev,
        Jason Gunthorpe <jgg@nvidia.com>,
        Joerg Roedel <joro@8bytes.org>, dmaengine@vger.kernel.org,
        vkoul@kernel.org
Cc:     Robin Murphy <robin.murphy@arm.com>, Will Deacon <will@kernel.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Raj Ashok <ashok.raj@intel.com>,
        "Tian, Kevin" <kevin.tian@intel.com>, Yi Liu <yi.l.liu@intel.com>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        "Zanussi, Tom" <tom.zanussi@intel.com>
References: <20230327232138.1490712-1-jacob.jun.pan@linux.intel.com>
 <20230327232138.1490712-5-jacob.jun.pan@linux.intel.com>
 <41d31adf-577e-431c-c400-2708885400c1@linux.intel.com>
From:   Vasant Hegde <vasant.hegde@amd.com>
In-Reply-To: <41d31adf-577e-431c-c400-2708885400c1@linux.intel.com>
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On 3/28/2023 10:50 AM, Baolu Lu wrote:
> On 3/28/23 7:21 AM, Jacob Pan wrote:
>> On VT-d platforms, RID_PASID is used for DMA request without PASID. We
>> should not treat RID_PASID special instead let it be allocated from the
>> global SVA PASID number space.
> 
> It's same to AMD and ARM SMMUv3, right? They also need an explicit
> reservation of PASID 0.

Yes for AMD driver. (Requests from the I/O device without a PASID are treated as
if they have PASID of 0).


-Vasant