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

Alexander Graf
2011-08-12T05:35:42Z

Am 12.08.2011 um 05:33 schrieb David Gibson <david@gibson.dropbear.id.au>:

> 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.

Well I'd like to keep Qemu out of the patching business, so the guest kernel would have to patch itself. But yes, PHyP guests can't run this target yet :). I'll take a stab at that too, but one continent at a time! ;)

Alex

>