Re: Question on context setup for passthrough

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2025/2/21 15:16, Jerry Snitselaar wrote:
> Hi Baolu,

Hi Jerry,

> 
> In context_setup_pass_through_cb there is a check that bails out
> if dev != &pdev->dev which doesn't exist in the code that sets up the
> context entries in the dma domain case. Is there a reason this check is
> done in the passthrough case?

The check "dev != &pdev->dev" was added to prevent setting a context for
a different device that has its own probe path.

> I've been looking at an issue where a vm is running with an
> intel-iommu device, and has a pcie-to-pci bridge with a device behind
> it. When running with this commit, and defaulting to passthrough it
> gets a DMAR fault for the present bit not being set in the context
> entry when the device is coming up, and the rid for the fault is the
> rid the bridge will use for transactions coming from the secondary bus.
> Without that check the context entry gets set up for that rid, and
> it doesn't get the DMAR fault.

This appears to be a bug. Do you have a fix, or can you tell me the
process I can use to reproduce this issue with a local setup?

Thanks,
baolu