[PATCH 18/19] KVM: PPC: Book3S HV: add passthrough support

[Benjamin Herrenschmidt]

On Tue, 2019-01-22 at 16:26 +1100, Paul Mackerras wrote:
> On Mon, Jan 07, 2019 at 08:10:05PM +0100, Cédric Le Goater wrote:
> > Clear the ESB pages from the VMA of the IRQ being pass through to the
> > guest and let the fault handler repopulate the VMA when the ESB pages
> > are accessed for an EOI or for a trigger.
> 
> Why do we want to do this?
> 
> I don't see any possible advantage to removing the PTEs from the
> userspace mapping.  You'll need to explain further.

Afaik bcs we change the mapping to point to the real HW irq ESB page
instead of the "IPI" that was there at VM init time.

Cedric, is that correct ?

Cheers,
Ben.