From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com [202.81.31.142]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e23smtp09.au.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id C6C062C019B for ; Wed, 1 May 2013 22:08:58 +1000 (EST) Received: from /spool/local by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 May 2013 21:59:28 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id DA21C2BB004F for ; Wed, 1 May 2013 22:08:51 +1000 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r41Bsx1Q5308428 for ; Wed, 1 May 2013 21:54:59 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r41C8pZe002130 for ; Wed, 1 May 2013 22:08:51 +1000 Date: Wed, 1 May 2013 21:36:43 +1000 From: David Gibson To: Simon Jeons Subject: Re: [PATCH -V7 18/18] powerpc: Update tlbie/tlbiel as per ISA doc Message-ID: <20130501113643.GA13041@truffula.fritz.box> References: <1367177859-7893-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1367177859-7893-19-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20130430061522.GC20202@truffula.fritz.box> <87ppxc9bpf.fsf@linux.vnet.ibm.com> <20130501052625.GC14106@truffula.fritz.box> <87hain9m5e.fsf@linux.vnet.ibm.com> <5180C9BE.5040002@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="a8Wt8u1KmwUX3Y2C" In-Reply-To: <5180C9BE.5040002@gmail.com> Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" , paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --a8Wt8u1KmwUX3Y2C Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, May 01, 2013 at 03:52:30PM +0800, Simon Jeons wrote: > On 05/01/2013 03:47 PM, Aneesh Kumar K.V wrote: > >David Gibson writes: > > > >>On Tue, Apr 30, 2013 at 10:51:00PM +0530, Aneesh Kumar K.V wrote: > >>>David Gibson writes: > >>> > >>>>On Mon, Apr 29, 2013 at 01:07:39AM +0530, Aneesh Kumar K.V wrote: > >>>>>From: "Aneesh Kumar K.V" > >>>>> > >>>>>Encode the actual page correctly in tlbie/tlbiel. This make sure we = handle > >>>>>multiple page size segment correctly. > >>>>As mentioned in previous comments, this commit message needs to give > >>>>much more detail about what precisely the existing implementation is > >>>>doing wrong. > >>>> > >>>>>Signed-off-by: Aneesh Kumar K.V > >>>>>--- > >>>>> arch/powerpc/mm/hash_native_64.c | 32 ++++++++++++++++++++++++++++= ++-- > >>>>> 1 file changed, 30 insertions(+), 2 deletions(-) > >>>>> > >>>>>diff --git a/arch/powerpc/mm/hash_native_64.c b/arch/powerpc/mm/hash= _native_64.c > >>>>>index bb920ee..6a2aead 100644 > >>>>>--- a/arch/powerpc/mm/hash_native_64.c > >>>>>+++ b/arch/powerpc/mm/hash_native_64.c > >>>>>@@ -61,7 +61,10 @@ static inline void __tlbie(unsigned long vpn, int= psize, int apsize, int ssize) > >>>>> switch (psize) { > >>>>> case MMU_PAGE_4K: > >>>>>+ /* clear out bits after (52) [0....52.....63] */ > >>>>>+ va &=3D ~((1ul << (64 - 52)) - 1); > >>>>> va |=3D ssize << 8; > >>>>>+ va |=3D mmu_psize_defs[apsize].sllp << 6; > >>>>> asm volatile(ASM_FTR_IFCLR("tlbie %0,0", PPC_TLBIE(%1,%0), %2) > >>>>> : : "r" (va), "r"(0), "i" (CPU_FTR_ARCH_206) > >>>>> : "memory"); > >>>>>@@ -69,9 +72,20 @@ static inline void __tlbie(unsigned long vpn, int= psize, int apsize, int ssize) > >>>>> default: > >>>>> /* We need 14 to 14 + i bits of va */ > >>>>> penc =3D mmu_psize_defs[psize].penc[apsize]; > >>>>>- va &=3D ~((1ul << mmu_psize_defs[psize].shift) - 1); > >>>>>+ va &=3D ~((1ul << mmu_psize_defs[apsize].shift) - 1); > >>>>> va |=3D penc << 12; > >>>>> va |=3D ssize << 8; > >>>>>+ /* Add AVAL part */ > >>>>>+ if (psize !=3D apsize) { > >>>>>+ /* > >>>>>+ * MPSS, 64K base page size and 16MB parge page size > >>>>>+ * We don't need all the bits, but rest of the bits > >>>>>+ * must be ignored by the processor. > >>>>>+ * vpn cover upto 65 bits of va. (0...65) and we need > >>>>>+ * 58..64 bits of va. > >>>>I can't understand what this comment is saying. Why do we need to do > >>>>something different in the psize !=3D apsize case? > >>>> > >>>>>+ */ > >>>>>+ va |=3D (vpn & 0xfe); > >>>>>+ } > >>>That is as per ISA doc. It says if base page size =3D=3D actual page s= ize, > >>>(RB)56:62 must be zeros, which must be ignored by the processor. > >>>Otherwise it should be filled with the selected bits of VA as explaine= d above. > >>What you've just said here makes much more sense than what's written > >>in the comment in the code. > >> > >>>We only support MPSS with base page size =3D 64K and actual page size = =3D 16MB. > >>Is that actually relevant to this code though? > >In a way yes. The number of bits we we select out of VA depends on the > >base page size and actual page size. We have a math around that > >documented in ISA. Now since we support only 64K and 16MB we can make it > >simpler by only selecting required bits and not making it a > >function. But then it is also not relevant to the code in that ISA also > >state other bits in (RB)56:62 must be zero. I wanted to capture both the > >details in the comment. >=20 > What's the benefit of ppc use hash-based page table instead of > tree-based page table? If you said that hash is faster, could x86 > change to it? Complex and debatable at best. But in any case it's a fixed property of the CPU, not something that can be changed in software. --=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 --a8Wt8u1KmwUX3Y2C Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlGA/ksACgkQaILKxv3ab8YqYwCfQ5m8QxptTuL5/F+cRO+vKn0I NEIAoIPi6jLee9OgPz/gfsoiXqi8xR5/ =t8SL -----END PGP SIGNATURE----- --a8Wt8u1KmwUX3Y2C--