[RFC PATCH v1] powerpc/prom_init: disable XIVE in Secure VM.

[Ram Pai]

On Thu, Mar 05, 2020 at 10:55:45AM +1100, David Gibson wrote:
> On Wed, Mar 04, 2020 at 04:56:09PM +0100, Cédric Le Goater wrote:
> > [ ... ]
> > 
> > > (1) applied the patch which shares the EQ-page with the hypervisor.
> > > (2) set "kernel_irqchip=off"
> > > (3) set "ic-mode=xive"
> > 
> > you don't have to set the interrupt mode. xive should be negotiated
> > by default.
> > 
> > > (4) set "svm=on" on the kernel command line.
> > > (5) no changes to the hypervisor and ultravisor.
> > > 
> > > And Boom it works!.   So you were right.
> > 
> > Excellent.
> >  
> > > I am sending out the patch for (1) above ASAP.
> > 
> > Next step, could you please try to do the same with the TIMA and ESB pfn ?
> > and use KVM.
> 
> I'm a bit confused by this.  Aren't the TIMA and ESB pages essentially
> IO pages, rather than memory pages from the guest's point of view?  I
> assume only memory pages are protected with PEF - I can't even really
> see what protecting an IO page would even mean.

It means, that the hypervisor and qemu cannot access the addresses used
to access the I/O pages. It can only be accessed by Ultravisor and the
SVM.

As it stands today, those pages are accessible from the hypervisor
and not from the SVM or the ultravisor.

To make it work, we need to enable acccess to those pages from the SVM
and from the ultravisor.  One thing I am not clear is should we block
access to those pages from the hypervisor.  If yes, than there is no
good way to do that, without hardware help.  If no, than those GPA pages
can be shared, so that hypervisor/ultravisor/qemu/SVM can all access
those pages.

RP