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

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Date:   Thu, 13 Jul 2017 13:37:04 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Balbir Singh <bsingharora@...il.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        dave.hansen@...el.com, hbabu@...ibm.com, arnd@...db.de,
        akpm@...ux-foundation.org, corbet@....net, mingo@...hat.com
Subject: Re: [RFC v5 14/38] powerpc: initial plumbing for key management

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@...ibm.com> 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.

RP