2014-10-15 23:44:36

by Kallol Biswas

Subject: PCIe PASID (Process Address Space ID) and iommu code

Resending, as message got bounced for html content.
--------------------------------------------
Hi,
PCIe has introduced PASID TLP Prefix. There are two ECNs on this.

It seems that AMD iommu code makes use of PASID. Is there a device that
utilizes this TLP prefix?

PASID allocation and management within a device is not clear to me. How
does device know which PASID to issue for which virtual address? Who makes
the association? Must be software/OS, but how? There is no table for this
like MSI-X table.

Any pointer/documentation will be appreciated.

Regards,

2014-10-16 03:51:21

by Bjorn Helgaas

Subject: Re: PCIe PASID (Process Address Space ID) and iommu code

[+cc Joerg, Suravee, Jay, iommu list, linux-pci]

On Wed, Oct 15, 2014 at 5:44 PM, Kallol Biswas <[email protected]> wrote:
> Resending, as message got bounced for html content.
> --------------------------------------------
> Hi,
> PCIe has introduced PASID TLP Prefix. There are two ECNs on this.
>
> It seems that AMD iommu code makes use of PASID. Is there a device that
> utilizes this TLP prefix?
>
> PASID allocation and management within a device is not clear to me. How
> does device know which PASID to issue for which virtual address? Who makes
> the association? Must be software/OS, but how? There is no table for this
> like MSI-X table.
>
> Any pointer/documentation will be appreciated.
>
> Regards,
> --
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2014-10-16 09:14:39

by Joerg Roedel

Subject: Re: PCIe PASID (Process Address Space ID) and iommu code

On Wed, Oct 15, 2014 at 09:50:58PM -0600, Bjorn Helgaas wrote:
> [+cc Joerg, Suravee, Jay, iommu list, linux-pci]
>
> On Wed, Oct 15, 2014 at 5:44 PM, Kallol Biswas <[email protected]> wrote:
> > Resending, as message got bounced for html content.
> > --------------------------------------------
> > Hi,
> > PCIe has introduced PASID TLP Prefix. There are two ECNs on this.
> >
> > It seems that AMD iommu code makes use of PASID. Is there a device that
> > utilizes this TLP prefix?

Yes, recent radeon GPUs can make use of the TLP prefix.

> > PASID allocation and management within a device is not clear to me. How
> > does device know which PASID to issue for which virtual address? Who makes
> > the association? Must be software/OS, but how? There is no table for this
> > like MSI-X table.

The setup of the PASIDs is device specific, so there is no standard for
setting up PASID address spaces on devices.


HTH,

Joerg