Re: [PATCH 09/10] KVM: PPC: Support SC1 hypercalls for PAPR in PR

David Gibson
2011-08-12T03:33:43Z

On Tue, Aug 09, 2011 at 06:31:47PM +0200, Alexander Graf wrote:
> PAPR defines hypercalls as SC1 instructions. Using these, the guest modifies
> page tables and does other privileged operations that it wouldn't be allowed
> to do in supervisor mode.
>
> This patch adds support for PR KVM to trap these instructions and route them
> through the same PAPR hypercall interface that we already use for HV style
> KVM.

This will work on a powermac or bare metal host. Unfortunately, it's
not enough on a pSeries LPAR host - the sc 1 instruction from the
guest problem state will go direct to the hypervisor, which will
return an error rather than trapping to the guest kernel.

The only way around this I can see is for qemu to search for and patch
up sc 1 instructions to something else. Obviously that would also
need some kernel support, and probably a capability to let it know if
it's necessary.

--
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_!