From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35603) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dmr9R-0000jT-F3 for qemu-devel@nongnu.org; Tue, 29 Aug 2017 20:46:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dmr9N-0000NU-Ed for qemu-devel@nongnu.org; Tue, 29 Aug 2017 20:46:37 -0400 Date: Wed, 30 Aug 2017 10:43:09 +1000 From: David Gibson Message-ID: <20170830004309.GA3386@umbus.fritz.box> References: <20170821200036.15036-1-bauerman@linux.vnet.ibm.com> <20170824025448.GA27401@fergus.ozlabs.ibm.com> <20170828175356.GB26893@ram.oc3035372033.ibm.com> <20170829014030.GD2578@umbus.fritz.box> <20170829163107.GC26893@ram.oc3035372033.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mYCpIKhGyMATD0i+" Content-Disposition: inline In-Reply-To: <20170829163107.GC26893@ram.oc3035372033.ibm.com> Subject: Re: [Qemu-devel] [PATCH] spapr: Add ibm, processor-storage-keys property to CPU DT node List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Ram Pai Cc: Paul Mackerras , Thiago Jung Bauermann , qemu-ppc@nongnu.org, qemu-devel@nongnu.org, Alexander Graf , Michael Ellerman --mYCpIKhGyMATD0i+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Aug 29, 2017 at 09:31:07AM -0700, Ram Pai wrote: > On Tue, Aug 29, 2017 at 11:40:30AM +1000, David Gibson wrote: > > On Mon, Aug 28, 2017 at 10:53:56AM -0700, Ram Pai wrote: > > > On Thu, Aug 24, 2017 at 12:54:48PM +1000, Paul Mackerras wrote: > > > >=20 > > > > We could either have two u16 fields for the number of keys for data > > > > and instruction, or we could have a u32 field for the number of keys > > > > and a separate bit in the flags field to indicate that instruction > > > > keys are supported. Which would be preferable? > > >=20 > > > the second choice is more confusion-proof; to me atleast. > > >=20 > > > The first choice gives a illusion that there are 'x' number of data k= eys > > > and 'y' number of instruction keys; which is not exactly true. > >=20 > > Ah.. can you elaborate? >=20 > On power8 and power9, there are only 32 keys, each key can be configured = to > disable data-access and instruction-access. The first choice, will > report 32 keys for data-access and 32 keys for instruction-access. To a > casual on-looker it gives an impresssion that there are 32 keys for > data-access and 32 keys for instruction-access; 64 keys in total. And > that is what I think can be the cause for confusion. Ah, I see. Paul, sorry, I hadn't realized the above when I said I preferred separate values for data and instr keys. In view of the above, I change my preference to a single # of keys and a flag that they can be used for instructions. --=20 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_! http://www.ozlabs.org/~dgibson --mYCpIKhGyMATD0i+ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAlmmChoACgkQbDjKyiDZ s5LRUw/+PMBnRS0AgJbaFU0tg+XQoksKQYyCMls8cNCEKaOZYK5MZHmJuOQshOpL xzxQjzKKof8Wc4uX7XzRDnl9wd1B+E0/dgnOZQTxxGzq2itWQ/cbcvOr1KZRZ/0T DQwKn5uHymV4J85782MSXHI6SL8H6ejrDK8ALz9J702feb9tSM3mlKOgzk2XwAWk /PaylXyo0xAi7qk8EPLWM6xO5V8WaxRsvUCMsB9+77cCMiyLpYFcIV+jQWbLp6HW 70xZV93Qt7usN7hbmiDjJvaW4z/KY9qIHffhgCusvcuUldgUaH2WyeFxzq7/e1op 0E+SovjTdne/4t6ZGASzxZpD43TACKaorb2fCXbgfVwhcRm+X8mlinD+vZHKpeq7 WdgqNLJKxuRU1TuJFLPaMCv/W6OebXAb04uYsAkoTIwdW5jtghrELt0YWTnlhLSg P7Phhcelqqkp4OAf3+mfR4c96K8V64PtoRBN5xdpuICdpUUkLdiIg6gtZsRXoc2Z lEej8/xbu59ZrwsLhiUu8sO+6vmtsODua13GipAnEs3nY5Cu9vM5bmJMDh0CsWlE 9lBuJGfSDvbmTESuy6+h91LjWiBT9ktQca2lQnSduyq+Vap+xHvN9u7/jLxAJpNu zg/SoMGNsTxQKLJ885V5LDvAGBhxzTyHYm3YyLlOk2dhRnVGA6A= =C0Q2 -----END PGP SIGNATURE----- --mYCpIKhGyMATD0i+--