From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752332AbcGARrK (ORCPT ); Fri, 1 Jul 2016 13:47:10 -0400 Received: from mga11.intel.com ([192.55.52.93]:30462 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751207AbcGARrI (ORCPT ); Fri, 1 Jul 2016 13:47:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,558,1459839600"; d="scan'208";a="998913965" Subject: [PATCH 4/4] x86: use pte_none() to test for empty PTE To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-mm@kvack.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, bp@alien8.de, ak@linux.intel.com, mhocko@suse.com, Dave Hansen From: Dave Hansen Date: Fri, 01 Jul 2016 10:47:07 -0700 References: <20160701174658.6ED27E64@viggo.jf.intel.com> In-Reply-To: <20160701174658.6ED27E64@viggo.jf.intel.com> Message-Id: <20160701174707.B9BBFAE8@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The page table manipulation code seems to have grown a couple of sites that are looking for empty PTEs. Just in case one of these entries got a stray bit set, use pte_none() instead of checking for a zero pte_val(). The use pte_same() makes me a bit nervous. If we were doing a pte_same() check against two cleared entries and one of them had a stray bit set, it might fail the pte_same() check. But, I don't think we ever _do_ pte_same() for cleared entries. It is almost entirely used for checking for races in fault-in paths. --- b/arch/x86/mm/init_64.c | 12 ++++++------ b/arch/x86/mm/pageattr.c | 2 +- b/arch/x86/mm/pgtable_32.c | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-) diff -puN arch/x86/mm/init_64.c~knl-strays-50-pte_val-cleanups arch/x86/mm/init_64.c --- a/arch/x86/mm/init_64.c~knl-strays-50-pte_val-cleanups 2016-07-01 10:42:07.781811987 -0700 +++ b/arch/x86/mm/init_64.c 2016-07-01 10:42:07.788812305 -0700 @@ -354,7 +354,7 @@ phys_pte_init(pte_t *pte_page, unsigned * pagetable pages as RO. So assume someone who pre-setup * these mappings are more intelligent. */ - if (pte_val(*pte)) { + if (!pte_none(*pte)) { if (!after_bootmem) pages++; continue; @@ -396,7 +396,7 @@ phys_pmd_init(pmd_t *pmd_page, unsigned continue; } - if (pmd_val(*pmd)) { + if (!pmd_none(*pmd)) { if (!pmd_large(*pmd)) { spin_lock(&init_mm.page_table_lock); pte = (pte_t *)pmd_page_vaddr(*pmd); @@ -470,7 +470,7 @@ phys_pud_init(pud_t *pud_page, unsigned continue; } - if (pud_val(*pud)) { + if (!pud_none(*pud)) { if (!pud_large(*pud)) { pmd = pmd_offset(pud, 0); last_map_addr = phys_pmd_init(pmd, addr, end, @@ -673,7 +673,7 @@ static void __meminit free_pte_table(pte for (i = 0; i < PTRS_PER_PTE; i++) { pte = pte_start + i; - if (pte_val(*pte)) + if (!pte_none(*pte)) return; } @@ -691,7 +691,7 @@ static void __meminit free_pmd_table(pmd for (i = 0; i < PTRS_PER_PMD; i++) { pmd = pmd_start + i; - if (pmd_val(*pmd)) + if (!pmd_none(*pmd)) return; } @@ -710,7 +710,7 @@ static bool __meminit free_pud_table(pud for (i = 0; i < PTRS_PER_PUD; i++) { pud = pud_start + i; - if (pud_val(*pud)) + if (!pud_none(*pud)) return false; } diff -puN arch/x86/mm/pageattr.c~knl-strays-50-pte_val-cleanups arch/x86/mm/pageattr.c --- a/arch/x86/mm/pageattr.c~knl-strays-50-pte_val-cleanups 2016-07-01 10:42:07.783812078 -0700 +++ b/arch/x86/mm/pageattr.c 2016-07-01 10:42:07.789812350 -0700 @@ -1185,7 +1185,7 @@ repeat: return __cpa_process_fault(cpa, address, primary); old_pte = *kpte; - if (!pte_val(old_pte)) + if (pte_none(old_pte)) return __cpa_process_fault(cpa, address, primary); if (level == PG_LEVEL_4K) { diff -puN arch/x86/mm/pgtable_32.c~knl-strays-50-pte_val-cleanups arch/x86/mm/pgtable_32.c --- a/arch/x86/mm/pgtable_32.c~knl-strays-50-pte_val-cleanups 2016-07-01 10:42:07.785812169 -0700 +++ b/arch/x86/mm/pgtable_32.c 2016-07-01 10:42:07.789812350 -0700 @@ -47,7 +47,7 @@ void set_pte_vaddr(unsigned long vaddr, return; } pte = pte_offset_kernel(pmd, vaddr); - if (pte_val(pteval)) + if (!pte_none(pteval)) set_pte_at(&init_mm, vaddr, pte, pteval); else pte_clear(&init_mm, vaddr, pte); _