On Mon, Aug 03, 2015 at 07:08:17PM +0200, Paolo Bonzini wrote: > > > On 03/08/2015 16:41, Andrew Jones wrote: > > Add enough RTAS support to support power-off, and apply it to > > exit(). > > > > Signed-off-by: Andrew Jones <drjo...@redhat.com> > > Why not use virtio-mmio + testdev on ppc as well? Similar to how we're > not using PSCI on ARM or ACPI on x86.
Strange as it seems, MMIO is actually a PITA for a simple pseries
guest like this. Basically, you have to enable the MMU - which
requires a whole bunch of setup - in order to perform cache-inhibited
loads and stores, which is what you need for IO.
There are hypercalls to sidestep this (H_LOGICAL_CI_LOAD and
H_LOGICAL_CI_STORE), but having a hypercall and KVM exit for every IO
access may be hideously slow.
In early development we did have a hypercall mediated virtio model,
but it was abandoned once we got PCI working.
--
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
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