Re: [Xen-users] Enabling SMMU for a bare metal guest

[Julien Grall <julien.grall@xxxxxxx>]

Hello Jarvis,

I have CCed Edgar who did the bring of Xen on Xilinx Zinqmp

On 21/06/16 15:40, Jarvis Roach wrote:
> I've been working on passing an ethernet controller through to a bare
> metal guest running on an Xilinx Z US+ MPSoC platform. I got it working,
> but only by using the system's physical address (PA) for DMA buffers and
> descriptors instead of using the guest's intermediate physical address
> (IPA), aka guest phyiscal address.
>
> I am aware of Julien's presentation on passthrough, and I am successful
> in passing the ethernet device through to a Linux guest, but when I
> follow the same steps for my bare metal guest, the IPA->PA translation
> doesn't seem to be happening. I would expect that if the SMMU was active
> for that ethernet controller then a) using PA for DMA buffers and
> descriptors should result in a translation fault, and b) using IPA for
> the same would work, neither of which is true.
Can you provide the guest configuration you are using?

> It seems to me that there is something extra is being done by, or for,
> the Linux guest that isn't done by, or for, my bare metal guest that
> enables the SMMU for that ethernet controller. I haven't been able to
> figure what that something extra is by searching the internet, reading
> through the available documentation, or digging into the code. Any help
> (better search terms, useful URLs, detailed description of the what's
> supposed to happen for guests generically or what actually happens for a
> Linux guest, a working bare metal example, etc) would be appreciated.
The SMMU is configured with Stage-2 page table and not exposed to the 
guest. I am not aware of any configuration required in the guest, except 
having a working network driver.
Regards,

--
Julien Grall

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