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

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From	Joerg Roedel <joro@8bytes.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] iommu/amd: Fix unity mapping initialization race
Date	Mon, 11 Jul 2016 09:30:01 +0200
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On Sun, Jul 10, 2016 at 07:40:53PM +0800, Wan Zongshun wrote:
> Do you mean we need enable the V and TV bits to DTE entry after all
> DTEs tables were initialized completely?

Yes, this is what my patch does and what fixes the bug that was
reported on machines which have unity-mapping entries.

> I checked this function 'init_device_table_dma', and find it just set
> V and TV bit, to set translation info valid and DTE bits127:1 valid.

Right, if no other bits are set this blocks all DMA from the gives
device-id.

> So I just think all things it should to do are to allow DMA access,
> GPA-to-SPA translation should be active, why you add function
> comments below is to not allow DMA access and suppress all page
> faults?
> 
> /*
>  * Init the device table to not allow DMA access for devices and
>  * suppress all page faults
>  */

Yeah, that comment needs to be updated. Not all DMA is blocked and
page-faults are not suppressed at all. Thanks for noticing.

	Joerg

Thread

[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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