From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752529AbeDFU67 (ORCPT ); Fri, 6 Apr 2018 16:58:59 -0400 Received: from mga07.intel.com ([134.134.136.100]:32372 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752205AbeDFU6M (ORCPT ); Fri, 6 Apr 2018 16:58:12 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,416,1517904000"; d="scan'208";a="32220631" Subject: [PATCH 09/11] x86/pti: enable global pages for shared areas To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Dave Hansen , aarcange@redhat.com, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, jgross@suse.com, x86@kernel.org, namit@vmware.com From: Dave Hansen Date: Fri, 06 Apr 2018 13:55:15 -0700 References: <20180406205501.24A1A4E7@viggo.jf.intel.com> In-Reply-To: <20180406205501.24A1A4E7@viggo.jf.intel.com> Message-Id: <20180406205515.2977EE7D@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen The entry/exit text and cpu_entry_area are mapped into userspace and the kernel. But, they are not _PAGE_GLOBAL. This creates unnecessary TLB misses. Add the _PAGE_GLOBAL flag for these areas. Signed-off-by: Dave Hansen Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Kees Cook Cc: Hugh Dickins Cc: Juergen Gross Cc: x86@kernel.org Cc: Nadav Amit --- b/arch/x86/mm/cpu_entry_area.c | 14 +++++++++++++- b/arch/x86/mm/pti.c | 23 ++++++++++++++++++++++- 2 files changed, 35 insertions(+), 2 deletions(-) diff -puN arch/x86/mm/cpu_entry_area.c~kpti-why-no-global arch/x86/mm/cpu_entry_area.c --- a/arch/x86/mm/cpu_entry_area.c~kpti-why-no-global 2018-04-06 10:47:58.246796118 -0700 +++ b/arch/x86/mm/cpu_entry_area.c 2018-04-06 10:47:58.252796118 -0700 @@ -27,8 +27,20 @@ EXPORT_SYMBOL(get_cpu_entry_area); void cea_set_pte(void *cea_vaddr, phys_addr_t pa, pgprot_t flags) { unsigned long va = (unsigned long) cea_vaddr; + pte_t pte = pfn_pte(pa >> PAGE_SHIFT, flags); - set_pte_vaddr(va, pfn_pte(pa >> PAGE_SHIFT, flags)); + /* + * The cpu_entry_area is shared between the user and kernel + * page tables. All of its ptes can safely be global. + * _PAGE_GLOBAL gets reused to help indicate PROT_NONE for + * non-present PTEs, so be careful not to set it in that + * case to avoid confusion. + */ + if (boot_cpu_has(X86_FEATURE_PGE) && + (pgprot_val(flags) & _PAGE_PRESENT)) + pte = pte_set_flags(pte, _PAGE_GLOBAL); + + set_pte_vaddr(va, pte); } static void __init diff -puN arch/x86/mm/pti.c~kpti-why-no-global arch/x86/mm/pti.c --- a/arch/x86/mm/pti.c~kpti-why-no-global 2018-04-06 10:47:58.248796118 -0700 +++ b/arch/x86/mm/pti.c 2018-04-06 10:47:58.252796118 -0700 @@ -300,6 +300,27 @@ pti_clone_pmds(unsigned long start, unsi return; /* + * Only clone present PMDs. This ensures only setting + * _PAGE_GLOBAL on present PMDs. This should only be + * called on well-known addresses anyway, so a non- + * present PMD would be a surprise. + */ + if (WARN_ON(!(pmd_flags(*pmd) & _PAGE_PRESENT))) + return; + + /* + * Setting 'target_pmd' below creates a mapping in both + * the user and kernel page tables. It is effectively + * global, so set it as global in both copies. Note: + * the X86_FEATURE_PGE check is not _required_ because + * the CPU ignores _PAGE_GLOBAL when PGE is not + * supported. The check keeps consistentency with + * code that only set this bit when supported. + */ + if (boot_cpu_has(X86_FEATURE_PGE)) + *pmd = pmd_set_flags(*pmd, _PAGE_GLOBAL); + + /* * Copy the PMD. That is, the kernelmode and usermode * tables will share the last-level page tables of this * address range @@ -348,7 +369,7 @@ static void __init pti_clone_entry_text( { pti_clone_pmds((unsigned long) __entry_text_start, (unsigned long) __irqentry_text_end, - _PAGE_RW | _PAGE_GLOBAL); + _PAGE_RW); } /* _