From: "Tian, Kevin" <kevin.tian@intel.com>
To: "Jiang, Dave" <dave.jiang@intel.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Joerg Roedel <joro@8bytes.org>,
Christoph Hellwig <hch@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jean-Philippe Brucker <jean-philippe@linaro.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
"Lu Baolu" <baolu.lu@linux.intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>, Barry Song <21cnbao@gmail.com>,
"Zanussi, Tom" <tom.zanussi@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>
Subject: RE: [PATCH 4/4] dmaengine: idxd: Use DMA API for in-kernel DMA with PASID
Date: Thu, 9 Dec 2021 02:06:27 +0000 [thread overview]
Message-ID: <BN9PR11MB5276EE8617A721EF20B07BCD8C709@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <5fec4e7e-be37-193b-b4ab-dd1bbdb589d1@intel.com>
> From: Jiang, Dave <dave.jiang@intel.com>
> Sent: Thursday, December 9, 2021 8:12 AM
> >>>
> >> Do you mean wq completion record address? It is already using DMA API.
> >> wq->compls = dma_alloc_coherent(dev, wq->compls_size,
> >> &wq->compls_addr, GFP_KERNEL);
> >> desc->compl_dma = wq->compls_addr + idxd->data->compl_size * i;
> > I would have expected something on the queue submission side too?
>
> DSA is different than typical DMA devices in the past. Instead of a
> software descriptor ring where the device DMA to fetch the descriptors
> after the software ringing a doorbell or writing a head index, the
> descriptors are submitted directly to the device via a CPU instruction
> (i.e. MOVDIR64B or ENQCMD(S)). The CPU takes the KVA of the 64B
> descriptor and writes to the device atomically. No DMA mapping is
> necessary in this case.
>
To be accurate, the cpu reads the 64B descriptor from KVA and
then write the descriptor to the device atomically.
next prev parent reply other threads:[~2021-12-09 2:06 UTC|newest]
Thread overview: 46+ 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 ` [PATCH 1/4] ioasid: Reserve a global PASID for in-kernel DMA Jacob Pan
2021-12-09 11:03 ` Jean-Philippe Brucker
2021-12-09 18:14 ` Jacob Pan
2021-12-10 9:06 ` Jean-Philippe Brucker
2021-12-10 12:31 ` Jason Gunthorpe
2021-12-10 18:05 ` Jacob Pan
2021-12-11 8:39 ` Tian, Kevin
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
2021-12-08 2:31 ` Lu Baolu
2021-12-08 18:49 ` Jacob Pan
2021-12-09 1:56 ` Tian, Kevin
2021-12-09 2:21 ` Lu Baolu
2021-12-09 16:32 ` Jacob Pan
2021-12-09 16:57 ` Raj, Ashok
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
2021-12-08 13:22 ` Jason Gunthorpe
2021-12-08 19:16 ` Jacob Pan
2021-12-09 2:32 ` Lu Baolu
2021-12-09 23:21 ` Jacob Pan
2021-12-09 23:41 ` Jason Gunthorpe
2021-12-10 6:46 ` Lu Baolu
2021-12-10 17:50 ` Jacob Pan
2021-12-10 17:48 ` Jason Gunthorpe
2021-12-10 18:18 ` Jacob Pan
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 23:27 ` Dave Jiang
2021-12-08 4:56 ` Vinod Koul
2021-12-08 17:36 ` Jacob Pan
2021-12-08 13:13 ` Jason Gunthorpe
2021-12-08 15:35 ` Dave Jiang
2021-12-08 17:51 ` Jason Gunthorpe
2021-12-09 1:48 ` Tian, Kevin
2021-12-09 19:18 ` Jacob Pan
2021-12-08 19:55 ` Jacob Pan
2021-12-08 20:30 ` Jason Gunthorpe
2021-12-08 21:59 ` Jacob Pan
2021-12-08 23:39 ` Jason Gunthorpe
2021-12-09 0:12 ` Dave Jiang
2021-12-09 2:06 ` Tian, Kevin [this message]
2021-12-08 18:37 ` kernel test robot
2021-12-08 13:10 ` [PATCH 0/4] Enable PASID for DMA API users Jason Gunthorpe
2021-12-08 18:15 ` Jacob Pan
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