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From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Barry Song <21cnbao@gmail.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
	iommu@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>,
	Christoph Hellwig <hch@infradead.org>,
	Lu Baolu <baolu.lu@linux.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>,
	mike.campin@intel.com, Yi Liu <yi.l.liu@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	jacob.jun.pan@linux.intel.com
Subject: Re: [RFC 0/7] Support in-kernel DMA with PASID and SVA
Date: Thu, 7 Oct 2021 12:11:27 -0700	[thread overview]
Message-ID: <20211007121127.53956635@jacob-builder> (raw)
In-Reply-To: <CAGsJ_4w+ed78cnJusM_enEZpdGghzvjgt0aYDPpfwk4z7PQqxQ@mail.gmail.com>

Hi Barry,

On Thu, 7 Oct 2021 18:43:33 +1300, Barry Song <21cnbao@gmail.com> wrote:

> > > Security-wise, KVA respects kernel mapping. So permissions are better
> > > enforced than pass-through and identity mapping.  
> >
> > Is this meaningful? Isn't the entire physical map still in the KVA and
> > isn't it entirely RW ?  
> 
> Some areas are RX, for example, ARCH64 supports KERNEL_TEXT_RDONLY.
> But the difference is really minor.
That brought up a good point if we were to use DMA API to give out KVA as
dma_addr for trusted devices. We cannot satisfy DMA direction requirements
since we can't change kernel mapping. It will be similar to DMA direct
where dir is ignored AFAICT.

Or we are saying if the device is trusted, using pass-through is allowed.
i.e. physical address.

Thoughts?

Thanks,

Jacob

WARNING: multiple messages have this Message-ID (diff)
From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Barry Song <21cnbao@gmail.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>,
	"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	iommu@lists.linux-foundation.org,
	Jason Gunthorpe <jgg@nvidia.com>,
	mike.campin@intel.com
Subject: Re: [RFC 0/7] Support in-kernel DMA with PASID and SVA
Date: Thu, 7 Oct 2021 12:11:27 -0700	[thread overview]
Message-ID: <20211007121127.53956635@jacob-builder> (raw)
In-Reply-To: <CAGsJ_4w+ed78cnJusM_enEZpdGghzvjgt0aYDPpfwk4z7PQqxQ@mail.gmail.com>

Hi Barry,

On Thu, 7 Oct 2021 18:43:33 +1300, Barry Song <21cnbao@gmail.com> wrote:

> > > Security-wise, KVA respects kernel mapping. So permissions are better
> > > enforced than pass-through and identity mapping.  
> >
> > Is this meaningful? Isn't the entire physical map still in the KVA and
> > isn't it entirely RW ?  
> 
> Some areas are RX, for example, ARCH64 supports KERNEL_TEXT_RDONLY.
> But the difference is really minor.
That brought up a good point if we were to use DMA API to give out KVA as
dma_addr for trusted devices. We cannot satisfy DMA direction requirements
since we can't change kernel mapping. It will be similar to DMA direct
where dir is ignored AFAICT.

Or we are saying if the device is trusted, using pass-through is allowed.
i.e. physical address.

Thoughts?

Thanks,

Jacob
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2021-10-07 19:07 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-21 20:29 [RFC 0/7] Support in-kernel DMA with PASID and SVA Jacob Pan
2021-09-21 20:29 ` Jacob Pan
2021-09-21 20:29 ` [RFC 1/7] ioasid: reserve special PASID for in-kernel DMA Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 2/7] dma-iommu: Add API for DMA request with PASID Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 3/7] iommu/vt-d: Add DMA w/ PASID support for PA and IOVA Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 4/7] dma-iommu: Add support for DMA w/ PASID in KVA Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 5/7] iommu/vt-d: Add support for KVA PASID mode Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 6/7] iommu: Add KVA map API Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-21 20:29 ` [RFC 7/7] dma/idxd: Use dma-iommu PASID API instead of SVA lib Jacob Pan
2021-09-21 20:29   ` Jacob Pan
2021-09-22 17:04 ` [RFC 0/7] Support in-kernel DMA with PASID and SVA Jason Gunthorpe
2021-09-22 17:04   ` Jason Gunthorpe via iommu
2021-09-29 19:37 ` Jacob Pan
2021-09-29 19:37   ` Jacob Pan
2021-09-29 19:39   ` Jason Gunthorpe
2021-09-29 19:39     ` Jason Gunthorpe via iommu
2021-09-29 22:57     ` Jacob Pan
2021-09-29 22:57       ` Jacob Pan
2021-09-29 23:43       ` Jason Gunthorpe
2021-09-29 23:43         ` Jason Gunthorpe via iommu
2021-09-30 14:22         ` Campin, Mike
2021-09-30 14:22           ` Campin, Mike
2021-09-30 15:21           ` Jacob Pan
2021-09-30 15:21             ` Jacob Pan
2021-10-01 12:24 ` Barry Song
2021-10-01 12:24   ` Barry Song
2021-10-01 12:36   ` Jason Gunthorpe
2021-10-01 12:36     ` Jason Gunthorpe via iommu
2021-10-01 12:45     ` Barry Song
2021-10-01 12:45       ` Barry Song
2021-10-04 16:40       ` Jacob Pan
2021-10-04 16:40         ` Jacob Pan
2021-10-04 18:21         ` Jason Gunthorpe
2021-10-04 18:21           ` Jason Gunthorpe via iommu
2021-10-07  5:43           ` Barry Song
2021-10-07  5:43             ` Barry Song
2021-10-07 11:32             ` Jason Gunthorpe
2021-10-07 11:32               ` Jason Gunthorpe via iommu
2021-10-07 11:54               ` Barry Song
2021-10-07 11:54                 ` Barry Song
2021-10-07 11:59                 ` Jason Gunthorpe
2021-10-07 11:59                   ` Jason Gunthorpe via iommu
2021-10-07 17:50                   ` Jacob Pan
2021-10-07 17:50                     ` Jacob Pan
2021-10-07 17:48                     ` Jason Gunthorpe
2021-10-07 17:48                       ` Jason Gunthorpe via iommu
2021-10-07 18:08                       ` Jacob Pan
2021-10-07 18:08                         ` Jacob Pan
2021-10-07 19:11             ` Jacob Pan [this message]
2021-10-07 19:11               ` Jacob Pan
2021-10-07 19:10               ` Jason Gunthorpe
2021-10-07 19:10                 ` Jason Gunthorpe via iommu

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