Re: [PATCH] iommu/vt-d: Add support for multiple DMA aliases

[David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

[-- Attachment #1.1: Type: text/plain, Size: 1629 bytes --]

On Fri, 2015-11-06 at 16:21 +0100, Jacek Lawrynowicz wrote:
> This patch solves IOMMU support issues with PCIe non-transparent bridges
> that use Requester ID look-up tables (LUT), e.g. PEX8733. Before exiting
> the bridge, packet's RID is rewritten according to LUT programmed by
> a driver. Modified packets are then passed to a destination bus and
> processed upstream. The problem is that such packets seem to come from
> non-existent nodes that are hidden behind NTB and are not discoverable
> by a destination node, so IOMMU discards them. Adding DMA alias for a
> given LUT entry allows IOMMU to create a proper mapping that enables
> inter-node communication.
> 
> The current DMA alias implementation supports only single alias, so it's
> not possible to connect more than two nodes when IOMMU is enabled. This
> implementation enables all possible aliases on a given bus (256) that
> are stored in a bitset. Alias devfn is directly translated to a bit
> number. The bitset is not allocated for devices that have no need for
> DMA aliases.
> 
> More details can be found in following article:
> http://www.plxtech.com/files/pdf/technical/expresslane/RTC_Enabling%20MulitHostSystemDesigns.pdf
> 
> Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Acked-by: David Woodhouse <David.Woodhouse-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Seems reasonable to me. Jörg?

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org                              Intel Corporation


[-- Attachment #1.2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5691 bytes --]

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]