From: Ram Pai <linuxram@us.ibm.com> To: Balbir Singh <bsingharora@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, dave.hansen@intel.com, hbabu@us.ibm.com, arnd@arndb.de, akpm@linux-foundation.org, corbet@lwn.net, mingo@redhat.com Subject: Re: [RFC v5 02/38] powerpc: Free up four 64K PTE bits in 64K backed HPTE pages Date: Tue, 11 Jul 2017 08:44:15 -0700 [thread overview] Message-ID: <20170711154415.GA5525@ram.oc3035372033.ibm.com> (raw) In-Reply-To: <20170711155959.79e2d4de@firefly.ozlabs.ibm.com> On Tue, Jul 11, 2017 at 03:59:59PM +1000, Balbir Singh wrote: > On Wed, 5 Jul 2017 14:21:39 -0700 > Ram Pai <linuxram@us.ibm.com> wrote: > > > Rearrange 64K PTE bits to free up bits 3, 4, 5 and 6 > > in the 64K backed HPTE pages. This along with the earlier > > patch will entirely free up the four bits from 64K PTE. > > The bit numbers are big-endian as defined in the ISA3.0 > > > > This patch does the following change to 64K PTE backed > > by 64K HPTE. > > > > H_PAGE_F_SECOND (S) which occupied bit 4 moves to the > > second part of the pte to bit 60. > > H_PAGE_F_GIX (G,I,X) which occupied bit 5, 6 and 7 also > > moves to the second part of the pte to bit 61, > > 62, 63, 64 respectively > > > > since bit 7 is now freed up, we move H_PAGE_BUSY (B) from > > bit 9 to bit 7. > > > > The second part of the PTE will hold > > (H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63. > > > > Before the patch, the 64K HPTE backed 64k PTE format was > > as follows > > > > 0 1 2 3 4 5 6 7 8 9 10...........................63 > > : : : : : : : : : : : : > > v v v v v v v v v v v v > > > > ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-, > > |x|x|x| |S |G |I |X |x|B|x|x|x|................|.|.|.|.| <- primary pte > > '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_' > > | | | | | | | | | | | | |..................| | | | | <- secondary pte > > '_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_' > > > > It's not entirely clear what the secondary pte contains > today and how many of the bits are free today? The secondary pte today is not used for anything for 64k-hpte backed ptes. It gets used the moment the pte gets backed by 4-k hptes. Till then the bits are available. And this patch makes use of that knowledge. Will add some words in the patch description towards this. Thanks, RP > > Balbir Singh. -- Ram Pai
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From: Ram Pai <linuxram@us.ibm.com> To: Balbir Singh <bsingharora@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, dave.hansen@intel.com, hbabu@us.ibm.com, arnd@arndb.de, akpm@linux-foundation.org, corbet@lwn.net, mingo@redhat.com Subject: Re: [RFC v5 02/38] powerpc: Free up four 64K PTE bits in 64K backed HPTE pages Date: Tue, 11 Jul 2017 08:44:15 -0700 [thread overview] Message-ID: <20170711154415.GA5525@ram.oc3035372033.ibm.com> (raw) In-Reply-To: <20170711155959.79e2d4de@firefly.ozlabs.ibm.com> On Tue, Jul 11, 2017 at 03:59:59PM +1000, Balbir Singh wrote: > On Wed, 5 Jul 2017 14:21:39 -0700 > Ram Pai <linuxram@us.ibm.com> wrote: > > > Rearrange 64K PTE bits to free up bits 3, 4, 5 and 6 > > in the 64K backed HPTE pages. This along with the earlier > > patch will entirely free up the four bits from 64K PTE. > > The bit numbers are big-endian as defined in the ISA3.0 > > > > This patch does the following change to 64K PTE backed > > by 64K HPTE. > > > > H_PAGE_F_SECOND (S) which occupied bit 4 moves to the > > second part of the pte to bit 60. > > H_PAGE_F_GIX (G,I,X) which occupied bit 5, 6 and 7 also > > moves to the second part of the pte to bit 61, > > 62, 63, 64 respectively > > > > since bit 7 is now freed up, we move H_PAGE_BUSY (B) from > > bit 9 to bit 7. > > > > The second part of the PTE will hold > > (H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63. > > > > Before the patch, the 64K HPTE backed 64k PTE format was > > as follows > > > > 0 1 2 3 4 5 6 7 8 9 10...........................63 > > : : : : : : : : : : : : > > v v v v v v v v v v v v > > > > ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-, > > |x|x|x| |S |G |I |X |x|B|x|x|x|................|.|.|.|.| <- primary pte > > '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_' > > | | | | | | | | | | | | |..................| | | | | <- secondary pte > > '_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_' > > > > It's not entirely clear what the secondary pte contains > today and how many of the bits are free today? The secondary pte today is not used for anything for 64k-hpte backed ptes. It gets used the moment the pte gets backed by 4-k hptes. Till then the bits are available. And this patch makes use of that knowledge. Will add some words in the patch description towards this. Thanks, RP > > Balbir Singh. -- Ram Pai -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-11 15:44 UTC|newest] Thread overview: 191+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-07-05 21:21 [RFC v5 00/38] powerpc: Memory Protection Keys Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 01/38] powerpc: Free up four 64K PTE bits in 4K backed HPTE pages Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-07 7:25 ` Balbir Singh 2017-07-07 7:25 ` Balbir Singh 2017-07-07 7:25 ` Balbir Singh 2017-07-05 21:21 ` [RFC v5 02/38] powerpc: Free up four 64K PTE bits in 64K " Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-11 5:59 ` Balbir Singh 2017-07-11 5:59 ` Balbir Singh 2017-07-11 15:44 ` Ram Pai [this message] 2017-07-11 15:44 ` Ram Pai 2017-07-12 3:10 ` Balbir Singh 2017-07-12 3:10 ` Balbir Singh 2017-07-13 7:39 ` Ram Pai 2017-07-13 7:39 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 03/38] powerpc: introduce pte_set_hash_slot() helper Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 04/38] powerpc: introduce pte_get_hash_gslot() helper Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 05/38] powerpc: capture the PTE format changes in the dump pte report Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 06/38] powerpc: use helper functions in __hash_page_64K() for 64K PTE Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 07/38] powerpc: use helper functions in __hash_page_huge() " Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 08/38] powerpc: use helper functions in __hash_page_4K() " Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 09/38] powerpc: use helper functions in __hash_page_4K() for 4K PTE Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 10/38] powerpc: use helper functions in flush_hash_page() Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 11/38] mm: introduce an additional vma bit for powerpc pkey Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-11 18:10 ` Dave Hansen 2017-07-11 18:10 ` Dave Hansen 2017-07-12 22:23 ` Ram Pai 2017-07-12 22:23 ` Ram Pai 2017-07-12 22:40 ` Benjamin Herrenschmidt 2017-07-12 22:40 ` Benjamin Herrenschmidt 2017-07-05 21:21 ` [RFC v5 12/38] mm: ability to disable execute permission on a key at creation Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-11 18:11 ` Dave Hansen 2017-07-11 18:11 ` Dave Hansen 2017-07-11 21:29 ` Benjamin Herrenschmidt 2017-07-11 21:29 ` Benjamin Herrenschmidt 2017-07-11 21:51 ` Ram Pai 2017-07-11 21:51 ` Ram Pai 2017-07-11 21:57 ` Dave Hansen 2017-07-11 21:57 ` Dave Hansen 2017-07-11 22:14 ` Ram Pai 2017-07-11 22:14 ` Ram Pai 2017-07-11 22:19 ` Dave Hansen 2017-07-11 22:19 ` Dave Hansen 2017-07-11 22:08 ` Benjamin Herrenschmidt 2017-07-11 22:08 ` Benjamin Herrenschmidt 2017-07-11 22:19 ` Ram Pai 2017-07-11 22:19 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 13/38] x86: disallow pkey creation with PKEY_DISABLE_EXECUTE Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-11 18:12 ` Dave Hansen 2017-07-11 18:12 ` Dave Hansen 2017-07-05 21:21 ` [RFC v5 14/38] powerpc: initial plumbing for key management Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-12 3:28 ` Balbir Singh 2017-07-12 3:28 ` Balbir Singh 2017-07-13 7:45 ` Ram Pai 2017-07-13 7:45 ` Ram Pai 2017-07-13 20:37 ` Ram Pai 2017-07-13 20:37 ` Ram Pai 2017-07-13 21:30 ` Balbir Singh 2017-07-13 21:30 ` Balbir Singh 2017-07-13 21:30 ` Balbir Singh 2017-07-13 21:30 ` Balbir Singh 2017-07-05 21:21 ` [RFC v5 15/38] powerpc: helper function to read,write AMR,IAMR,UAMOR registers Ram Pai 2017-07-05 21:21 ` [RFC v5 15/38] powerpc: helper function to read, write AMR, IAMR, UAMOR registers Ram Pai 2017-07-05 21:21 ` [RFC v5 15/38] powerpc: helper function to read,write AMR,IAMR,UAMOR registers Ram Pai 2017-07-12 5:26 ` Balbir Singh 2017-07-12 5:26 ` Balbir Singh 2017-07-13 7:55 ` Ram Pai 2017-07-13 7:55 ` Ram Pai 2017-07-13 9:49 ` Balbir Singh 2017-07-13 9:49 ` Balbir Singh 2017-07-13 9:49 ` Balbir Singh 2017-07-13 23:29 ` Ram Pai 2017-07-13 23:29 ` Ram Pai 2017-07-13 23:29 ` Ram Pai 2017-07-13 23:29 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 16/38] powerpc: implementation for arch_set_user_pkey_access() Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 17/38] powerpc: sys_pkey_alloc() and sys_pkey_free() system calls Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 18/38] powerpc: store and restore the pkey state across context switches Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 19/38] powerpc: introduce execute-only pkey Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 20/38] powerpc: ability to associate pkey to a vma Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 21/38] powerpc: implementation for arch_override_mprotect_pkey() Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:21 ` [RFC v5 22/38] powerpc: map vma key-protection bits to pte key bits Ram Pai 2017-07-05 21:21 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 23/38] powerpc: sys_pkey_mprotect() system call Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 24/38] powerpc: Program HPTE key protection bits Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 25/38] powerpc: helper to validate key-access permissions of a pte Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 26/38] powerpc: check key protection for user page access Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 27/38] powerpc: Macro the mask used for checking DSI exception Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 28/38] powerpc: implementation for arch_vma_access_permitted() Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 29/38] powerpc: Handle exceptions caused by pkey violation Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 30/38] powerpc: capture AMR register content on " Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 31/38] powerpc: introduce get_pte_pkey() helper Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-10 3:11 ` Anshuman Khandual 2017-07-10 3:11 ` Anshuman Khandual 2017-07-10 5:55 ` Ram Pai 2017-07-10 5:55 ` Ram Pai 2017-07-11 11:22 ` Anshuman Khandual 2017-07-11 11:22 ` Anshuman Khandual 2017-07-05 21:22 ` [RFC v5 32/38] powerpc: capture the violated protection key on fault Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-10 3:10 ` Anshuman Khandual 2017-07-10 3:10 ` Anshuman Khandual 2017-07-10 5:49 ` Ram Pai 2017-07-10 5:49 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 33/38] powerpc: Deliver SEGV signal on pkey violation Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-10 3:08 ` Anshuman Khandual 2017-07-10 3:08 ` Anshuman Khandual 2017-07-05 21:22 ` [RFC v5 34/38] procfs: display the protection-key number associated with a vma Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-10 3:07 ` Anshuman Khandual 2017-07-10 3:07 ` Anshuman Khandual 2017-07-10 6:01 ` Ram Pai 2017-07-10 6:01 ` Ram Pai 2017-07-11 18:13 ` Dave Hansen 2017-07-11 18:13 ` Dave Hansen 2017-07-13 8:03 ` Ram Pai 2017-07-13 8:03 ` Ram Pai 2017-07-13 14:07 ` Dave Hansen 2017-07-13 14:07 ` Dave Hansen 2017-07-13 17:04 ` Ram Pai 2017-07-13 17:04 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 35/38] selftest: Move protecton key selftest to arch neutral directory Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 36/38] selftest: PowerPC specific test updates to memory protection keys Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-11 17:33 ` Dave Hansen 2017-07-11 17:33 ` Dave Hansen 2017-07-12 21:57 ` Ram Pai 2017-07-12 21:57 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 37/38] Documentation: Move protecton key documentation to arch neutral directory Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-05 21:22 ` [RFC v5 38/38] Documentation: PowerPC specific updates to memory protection keys Ram Pai 2017-07-05 21:22 ` Ram Pai 2017-07-10 3:07 ` Anshuman Khandual 2017-07-10 3:07 ` Anshuman Khandual 2017-07-10 5:59 ` Ram Pai 2017-07-10 5:59 ` Ram Pai 2017-07-11 18:23 ` Dave Hansen 2017-07-11 18:23 ` Dave Hansen 2017-07-13 19:56 ` Ram Pai 2017-07-13 19:56 ` Ram Pai 2017-07-10 5:43 ` [RFC v5 00/38] powerpc: Memory Protection Keys Anshuman Khandual 2017-07-10 5:43 ` Anshuman Khandual 2017-07-10 6:05 ` Ram Pai 2017-07-10 6:05 ` Ram Pai 2017-07-10 17:15 ` Ram Pai 2017-07-10 17:15 ` Ram Pai 2017-07-11 14:52 ` Michal Hocko 2017-07-11 14:52 ` Michal Hocko 2017-07-11 19:32 ` Ram Pai 2017-07-11 19:32 ` Ram Pai 2017-07-11 21:30 ` Benjamin Herrenschmidt 2017-07-11 21:30 ` Benjamin Herrenschmidt 2017-07-12 7:23 ` Michal Hocko 2017-07-12 7:23 ` Michal Hocko 2017-07-12 7:39 ` Michal Hocko 2017-07-12 7:39 ` Michal Hocko 2017-07-12 22:53 ` Benjamin Herrenschmidt 2017-07-12 22:53 ` Benjamin Herrenschmidt 2017-07-13 6:20 ` Michal Hocko 2017-07-13 6:20 ` Michal Hocko
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