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From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	iommu@lists.linux-foundation.org,
	Jacob Pan <jacob.jun.pan@intel.com>,
	Jason Gunthorpe <jgg@nvidia.com>, Barry Song <21cnbao@gmail.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	"Zanussi, Tom" <tom.zanussi@intel.com>
Subject: Re: [PATCH 2/4] iommu: Add PASID support for DMA mapping API users
Date: Wed, 8 Dec 2021 10:49:39 -0800	[thread overview]
Message-ID: <20211208104939.732fa5b9@jacob-builder> (raw)
In-Reply-To: <16408193-c8bc-3046-b32f-9274bf0b415c@linux.intel.com>

Hi Lu,

On Wed, 8 Dec 2021 10:31:36 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> Hi Jacob,
> 
> On 12/7/21 9:47 PM, Jacob Pan wrote:
> > DMA mapping API is the de facto standard for in-kernel DMA. It operates
> > on a per device/RID basis which is not PASID-aware.
> > 
> > Some modern devices such as Intel Data Streaming Accelerator, PASID is
> > required for certain work submissions. To allow such devices use DMA
> > mapping API, we need the following functionalities:
> > 1. Provide device a way to retrieve a kernel PASID for work submission
> > 2. Enable the kernel PASID on the IOMMU
> > 3. Establish address space for the kernel PASID that matches the default
> >     domain. Let it be IOVA or physical address in case of pass-through.
> > 
> > This patch introduces a driver facing API that enables DMA API
> > PASID usage. Once enabled, device drivers can continue to use DMA APIs
> > as is. There is no difference in dma_handle between without PASID and
> > with PASID.  
> 
> Can a device issue DMA requests with PASID even there's no system IOMMU
> or the system IOMMU is disabled?
> 
Good point. 
If IOMMU is not enabled, device cannot issue DMA requests with PASID. This
API will not be available. Forgot to add dummy functions to the header.

> Best regards,
> baolu


Thanks,

Jacob
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WARNING: multiple messages have this Message-ID (diff)
From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: <iommu@lists.linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>, Jason Gunthorpe <jgg@nvidia.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Jacob Pan <jacob.jun.pan@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
	"Dave Jiang" <dave.jiang@intel.com>,
	Tony Luck <tony.luck@intel.com>, Yi Liu <yi.l.liu@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	Barry Song <21cnbao@gmail.com>,
	"Zanussi, Tom" <tom.zanussi@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH 2/4] iommu: Add PASID support for DMA mapping API users
Date: Wed, 8 Dec 2021 10:49:39 -0800	[thread overview]
Message-ID: <20211208104939.732fa5b9@jacob-builder> (raw)
In-Reply-To: <16408193-c8bc-3046-b32f-9274bf0b415c@linux.intel.com>

Hi Lu,

On Wed, 8 Dec 2021 10:31:36 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> Hi Jacob,
> 
> On 12/7/21 9:47 PM, Jacob Pan wrote:
> > DMA mapping API is the de facto standard for in-kernel DMA. It operates
> > on a per device/RID basis which is not PASID-aware.
> > 
> > Some modern devices such as Intel Data Streaming Accelerator, PASID is
> > required for certain work submissions. To allow such devices use DMA
> > mapping API, we need the following functionalities:
> > 1. Provide device a way to retrieve a kernel PASID for work submission
> > 2. Enable the kernel PASID on the IOMMU
> > 3. Establish address space for the kernel PASID that matches the default
> >     domain. Let it be IOVA or physical address in case of pass-through.
> > 
> > This patch introduces a driver facing API that enables DMA API
> > PASID usage. Once enabled, device drivers can continue to use DMA APIs
> > as is. There is no difference in dma_handle between without PASID and
> > with PASID.  
> 
> Can a device issue DMA requests with PASID even there's no system IOMMU
> or the system IOMMU is disabled?
> 
Good point. 
If IOMMU is not enabled, device cannot issue DMA requests with PASID. This
API will not be available. Forgot to add dummy functions to the header.

> Best regards,
> baolu


Thanks,

Jacob

  reply	other threads:[~2021-12-08 18:45 UTC|newest]

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-07 13:47 [PATCH 0/4] Enable PASID for DMA API users Jacob Pan
2021-12-07 13:47 ` Jacob Pan
2021-12-07 13:47 ` [PATCH 1/4] ioasid: Reserve a global PASID for in-kernel DMA Jacob Pan
2021-12-07 13:47   ` Jacob Pan
2021-12-09 11:03   ` Jean-Philippe Brucker
2021-12-09 11:03     ` Jean-Philippe Brucker
2021-12-09 18:14     ` Jacob Pan
2021-12-09 18:14       ` Jacob Pan
2021-12-10  9:06       ` Jean-Philippe Brucker
2021-12-10  9:06         ` Jean-Philippe Brucker
2021-12-10 12:31         ` Jason Gunthorpe via iommu
2021-12-10 12:31           ` Jason Gunthorpe
2021-12-10 18:05           ` Jacob Pan
2021-12-10 18:05             ` Jacob Pan
2021-12-11  8:39             ` Tian, Kevin
2021-12-11  8:39               ` Tian, Kevin
2021-12-12 23:34               ` Jason Gunthorpe via iommu
2021-12-12 23:34                 ` Jason Gunthorpe
2021-12-07 13:47 ` [PATCH 2/4] iommu: Add PASID support for DMA mapping API users Jacob Pan
2021-12-07 13:47   ` Jacob Pan
2021-12-08  2:31   ` Lu Baolu
2021-12-08  2:31     ` Lu Baolu
2021-12-08 18:49     ` Jacob Pan [this message]
2021-12-08 18:49       ` Jacob Pan
2021-12-09  1:56       ` Tian, Kevin
2021-12-09  1:56         ` Tian, Kevin
2021-12-09  2:21         ` Lu Baolu
2021-12-09  2:21           ` Lu Baolu
2021-12-09 16:32           ` Jacob Pan
2021-12-09 16:32             ` Jacob Pan
2021-12-09 16:57             ` Raj, Ashok
2021-12-09 16:57               ` Raj, Ashok
2021-12-09 17:34               ` Jacob Pan
2021-12-09 17:34                 ` Jacob Pan
2021-12-07 13:47 ` [PATCH 3/4] iommu/vt-d: Support PASID DMA for in-kernel usage Jacob Pan
2021-12-07 13:47   ` Jacob Pan
2021-12-08 13:22   ` Jason Gunthorpe via iommu
2021-12-08 13:22     ` Jason Gunthorpe
2021-12-08 19:16     ` Jacob Pan
2021-12-08 19:16       ` Jacob Pan
2021-12-09  2:32       ` Lu Baolu
2021-12-09  2:32         ` Lu Baolu
2021-12-09 23:21         ` Jacob Pan
2021-12-09 23:21           ` Jacob Pan
2021-12-09 23:41           ` Jason Gunthorpe via iommu
2021-12-09 23:41             ` Jason Gunthorpe
2021-12-10  6:46           ` Lu Baolu
2021-12-10  6:46             ` Lu Baolu
2021-12-10 17:50             ` Jacob Pan
2021-12-10 17:50               ` Jacob Pan
2021-12-10 17:48               ` Jason Gunthorpe via iommu
2021-12-10 17:48                 ` Jason Gunthorpe
2021-12-10 18:18                 ` Jacob Pan
2021-12-10 18:18                   ` Jacob Pan
2021-12-10 18:53                   ` Jason Gunthorpe via iommu
2021-12-10 18:53                     ` Jason Gunthorpe
2021-12-07 13:47 ` [PATCH 4/4] dmaengine: idxd: Use DMA API for in-kernel DMA with PASID Jacob Pan
2021-12-07 13:47   ` Jacob Pan
2021-12-07 23:27   ` Dave Jiang
2021-12-07 23:27     ` Dave Jiang
2021-12-08  4:56     ` Vinod Koul
2021-12-08  4:56       ` Vinod Koul
2021-12-08 17:36       ` Jacob Pan
2021-12-08 17:36         ` Jacob Pan
2021-12-08 13:13   ` Jason Gunthorpe via iommu
2021-12-08 13:13     ` Jason Gunthorpe
2021-12-08 15:35     ` Dave Jiang
2021-12-08 15:35       ` Dave Jiang
2021-12-08 17:51       ` Jason Gunthorpe via iommu
2021-12-08 17:51         ` Jason Gunthorpe
2021-12-09  1:48         ` Tian, Kevin
2021-12-09  1:48           ` Tian, Kevin
2021-12-09 19:18           ` Jacob Pan
2021-12-09 19:18             ` Jacob Pan
2021-12-08 19:55     ` Jacob Pan
2021-12-08 19:55       ` Jacob Pan
2021-12-08 20:30       ` Jason Gunthorpe via iommu
2021-12-08 20:30         ` Jason Gunthorpe
2021-12-08 21:59         ` Jacob Pan
2021-12-08 21:59           ` Jacob Pan
2021-12-08 23:39           ` Jason Gunthorpe via iommu
2021-12-08 23:39             ` Jason Gunthorpe
2021-12-09  0:12             ` Dave Jiang
2021-12-09  0:12               ` Dave Jiang
2021-12-09  2:06               ` Tian, Kevin
2021-12-09  2:06                 ` Tian, Kevin
2021-12-08 18:37   ` kernel test robot
2021-12-08 18:37     ` kernel test robot
2021-12-08 18:37     ` kernel test robot
2021-12-08 13:10 ` [PATCH 0/4] Enable PASID for DMA API users Jason Gunthorpe via iommu
2021-12-08 13:10   ` Jason Gunthorpe
2021-12-08 18:15   ` Jacob Pan
2021-12-08 18:15     ` Jacob Pan

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