Re: [RFC v5 14/38] powerpc: initial plumbing for key management

[Balbir Singh]

On Fri, Jul 14, 2017 at 6:37 AM, Ram Pai <linuxram@xxxxxxxxxx> wrote:
> On Thu, Jul 13, 2017 at 12:45:00AM -0700, Ram Pai wrote:
>> On Wed, Jul 12, 2017 at 01:28:25PM +1000, Balbir Singh wrote:
>> > On Wed,  5 Jul 2017 14:21:51 -0700
>> > Ram Pai <linuxram@xxxxxxxxxx> wrote:
>> >
>> > > Initial plumbing to manage all the keys supported by the
>> > > hardware.
>> > >
>> > > Total 32 keys are supported on powerpc. However pkey 0,1
>> > > and 31 are reserved. So effectively we have 29 pkeys.
>> > >
>> > > This patch keeps track of reserved keys, allocated  keys
>> > > and keys that are currently free.
>> >
>> > It looks like this patch will only work in guest mode?
>> > Is that an assumption we've made? What happens if I use
>> > keys when running in hypervisor mode?
>>
>> It works in supervisor mode, as a guest aswell as a bare-metal
>> kernel. Whatever needs to be done in hypervisor mode
>> is already there in power-kvm.
>
> I realize i did not answer your question accurately...
> "What happens if I use keys when running in hypervisor mode?"
>
> Its not clear what happens. As far as I can tell the MMU does
> not check key violation when in hypervisor mode. So effectively
> I think, keys are ineffective when in hypervisor mode.

keys are honored in hypervisor mode. I was just
stating that we need a mechanism used by the hypervisor
to partition the key space between guests and hypervisor.

Balbir Singh