On 27/02/2025 6:28 pm, Jason Andryuk wrote: > On 2025-02-27 05:23, Roger Pau Monné wrote: >>> To work around this, we can, for per-device IRTs, program the hardware >>> to use the guest data & associated IRTE. The address doesn't matter >>> since the IRTE handles that, and the Xen address & vector can be >>> used as >>> expected. >> >> All this work on AMD because when interrupt remapping is enabled all >> MSIs are handled by the remapping table, while on Intel there's still >> a bit in the MSI address field to signal whether the MSI is using a >> remapping entry, or is using the "compatibility" format (iow: no >> remapping). > > So, on Intel, if the guest hands the device the MSI address, it can > decided to bypass remapping? > > Thanks for providing insight into the Intel inner workings. That's > why I am asking.
Yes. In the IOMMU you can choose between blocking or permitting compatibility-form interrupts, but you can't cause them to become remapped. ~Andrew
