From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id B8F5C6B0261 for ; Thu, 7 Jul 2016 20:19:19 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id e189so65331382pfa.2 for ; Thu, 07 Jul 2016 17:19:19 -0700 (PDT) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTP id zf8si747057pac.177.2016.07.07.17.19.15 for ; Thu, 07 Jul 2016 17:19:16 -0700 (PDT) Subject: [PATCH 4/4] x86: use pte_none() to test for empty PTE From: Dave Hansen Date: Thu, 07 Jul 2016 17:19:15 -0700 References: <20160708001909.FB2443E2@viggo.jf.intel.com> In-Reply-To: <20160708001909.FB2443E2@viggo.jf.intel.com> Message-Id: <20160708001915.813703D9@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: 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@intel.com, Dave Hansen , dave.hansen@linux.intel.com From: Dave Hansen 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. Signed-off-by: Dave Hansen --- 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 2016-07-07 17:17:44.942808493 -0700 +++ b/arch/x86/mm/init_64.c 2016-07-07 17:17:44.949808807 -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 2016-07-07 17:17:44.944808582 -0700 +++ b/arch/x86/mm/pageattr.c 2016-07-07 17:17:44.950808852 -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 2016-07-07 17:17:44.946808672 -0700 +++ b/arch/x86/mm/pgtable_32.c 2016-07-07 17:17:44.950808852 -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); _ -- 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: email@kvack.org