[PATCH 00/19] KVM: PPC: Book3S HV: add XIVE native exploitation mode

[David Gibson]

On Wed, Feb 06, 2019 at 09:13:15AM +1100, Paul Mackerras wrote:
> On Tue, Feb 05, 2019 at 12:31:28PM +0100, Cédric Le Goater wrote:
> > >>> As for nesting, I suggest for the foreseeable future we stick to XICS
> > >>> emulation in nested guests.
> > >>
> > >> ok. so no kernel_irqchip at all. hmm. 
> > 
> > I was confused with what Paul calls 'XICS emulation'. It's not the QEMU
> > XICS emulated device but the XICS-over-XIVE KVM device, the KVM XICS 
> > device KVM uses when under a P9 processor. 
> 
> Actually there are two separate implementations of XICS emulation in
> KVM.  The first (older) one is almost entirely a software emulation
> but does have some cases where it accesses an underlying XICS device
> in order to make some things faster (IPIs and pass-through of a device
> interrupt to a guest).  The other, newer one is the XICS-on-XIVE
> emulation that Ben wrote, which uses the XIVE hardware pretty heavily.
> My patch was about making the the older code work when there is no
> XICS available to the host.

Ah, right.  To clarify my earlier statements in light of this:

 * We definitely want some sort of kernel-XICS available in a nested
   guest.  AIUI, this is now accomplished, so, Yay!

 * Implementing the L2 XICS in terms of L1's PAPR-XIVE would be a
   bonus, but it's a much lower priority.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://lists.ozlabs.org/pipermail/linuxppc-dev/attachments/20190206/29bd892c/attachment.sig>