On 2/11/19 7:42 AM, Benjamin Herrenschmidt wrote:

On Mon, 2019-02-11 at 13:38 +1100, David Gibson wrote:

quoted

1) All in kernel

The offset always maps directly to guest irq number and the kernel
somehow binds it either to an IPI or a host irq as necessary.
Cédric's original code attempts this, but the mechanism of keeping a
pointer to the VMA can't work.

Why do you need a pointer to the VMA anyway ? unmap_mapping_range()
doesn't need a VMA for the unmap part, and faults/mmaps have the VMA.

quoted

But.. remapping the irqs should be sufficiently infrequent that it
might be ok to consider simply stepping through all the hosting
process's VMAs to do this.

Which unmap_mapping_range() does for you as I explained previously. You
only need the address space. See how spufs does it (among others).

and the different CAPI drivers. This is much better and it works fine.

On the same topic, the XIVE IC on P10 will use IPI ESB pages for the 
PHB interrupts sources. We will still need this kind of remapping but 
the pages will be from the same controller.

Thanks,

C.