Re: [RFC PATCH 01/10] KVM: PPC: BOOK3S: PR: Fix PURR and SPURR emulation

On Fri, Jan 31, 2014 at 11:47:44AM +0100, Alexander Graf wrote:

On 31.01.2014, at 11:38, Aneesh Kumar K.V [off-list ref] wrote:

quoted

Alexander Graf [off-list ref] writes:

quoted

On 01/28/2014 05:44 PM, Aneesh Kumar K.V wrote:

quoted

We definitely don't need to emulate mtspr, because both the registers
are hypervisor resource.

This patch description doesn't cover what the patch actually does. It 
changes the implementation from "always tell the guest it uses 100%" to 
"give the guest an accurate amount of cpu time spent inside guest
context".

Will fix that

quoted

Also, I think we either go with full hyp semantics which means we also 
emulate the offset or we go with no hyp awareness in the guest at all 
which means we also don't emulate SPURR which is a hyp privileged
register.

Can you clarify this ?

In the 2.06 ISA SPURR is hypervisor privileged. That changed for 2.07 where it became supervisor privileged. So I suppose your patch is ok. When reviewing those patches I only had 2.06 around because power.org was broken.

It's always been supervisor privilege for reading and hypervisor
privilege for writing, ever since it was introduced in 2.05, and that
hasn't changed.  So I think what Aneesh is doing is correct.

Regards,
Paul.