Re: [PATCH] iommu/amd: Fix unity mapping initialization race

From	Wan ZongShun <mcuos.com@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] iommu/amd: Fix unity mapping initialization race
Date	2016-07-11 12:10 +0200
Message-ID	<rTGk2-5Co-19@gated-at.bofh.it> (permalink)
References	<rRXyG-2Wq-35@gated-at.bofh.it> <rTlpf-6S-9@gated-at.bofh.it> <rTDPb-3Uh-1@gated-at.bofh.it> <rTFHj-55x-13@gated-at.bofh.it> <rTFQZ-59c-7@gated-at.bofh.it>
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>
>> Sorry, why you still say this 'init_device_table_dma' can block DMA?
>> I just think this function will enable DMA transfer, since  we set
>> the V and TV bits, right? or I misunderstand what "block DMA" mean?
>
> When the V and TV bits are not set, it means that all DMA from that
> device-id is forwared untranslated by the IOMMU. But if we set V and TV
> it means that there is translation information, and the IOMMU translates
> the requests using the rest of the DTE information. As all other bits
> are 0, this means that page-table-level is 0 (== no page-table) and that
> the global IW and IR bits are 0 too (== no read and write permissions).
> So all requests are blocked.
>

Clearly.

Thanks.

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



-- 
---
Vincent Wan(Zongshun)
www.mcuos.com

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[PATCH] iommu/amd: Fix unity mapping initialization race Joerg Roedel <joro@8bytes.org> - 2016-07-06 18:10 +0200
  Re: [PATCH] iommu/amd: Fix unity mapping initialization race Wan Zongshun <vw@iommu.org> - 2016-07-10 13:50 +0200
    Re: [PATCH] iommu/amd: Fix unity mapping initialization race Joerg Roedel <joro@8bytes.org> - 2016-07-11 09:30 +0200
      Re: [PATCH] iommu/amd: Fix unity mapping initialization race Wan Zongshun <vw@iommu.org> - 2016-07-11 11:30 +0200
        Re: [PATCH] iommu/amd: Fix unity mapping initialization race Joerg Roedel <joro@8bytes.org> - 2016-07-11 11:40 +0200
          Re: [PATCH] iommu/amd: Fix unity mapping initialization race Wan ZongShun <mcuos.com@gmail.com> - 2016-07-11 12:10 +0200

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