From: Jason Gunthorpe <jgg@nvidia.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
"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>,
"Jiang, Dave" <dave.jiang@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 1/4] ioasid: Reserve a global PASID for in-kernel DMA
Date: Sun, 12 Dec 2021 19:34:28 -0400 [thread overview]
Message-ID: <20211212233428.GM6385@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB5276CDA4303C18369178DECF8C729@BN9PR11MB5276.namprd11.prod.outlook.com>
On Sat, Dec 11, 2021 at 08:39:12AM +0000, Tian, Kevin wrote:
> Uniqueness is not the main argument of using global PASIDs for
> SWQ, since it can be defined either in per-RID or in global PASID
> space. No SVA architecture can allow two processes to use the
> same PASID to submit work unless they share mm! 😊
>
> IMO the real reason is that SWQ for user SVA must be accessed
> via ENQCMD instruction which fetches the PASID from a CPU MSR
This really should have been inside a comment in the struct mm
"pasid is the value used by x86 ENQCMD"
(and if we phrase it that way I wonder why it is in a struct mm not
some process or task related struct, since it has nothing to do with
page tables)
And, IMHO, the IOMMU part of the code should avoid using this
field. IOMMU should be able to create arbitarily many "SVA"
iommu_domains for use by PASID even if they can't be used with
ENQCMD. Such is proper layering.
Jason
next prev parent reply other threads:[~2021-12-12 23:35 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 [this message]
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
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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