Commit-ID: 0f561fce4d6979a50415616896512f87a6d1d5c8
Gitweb: https://git.kernel.org/tip/0f561fce4d6979a50415616896512f87a6d1d5c8
Author: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 6 Apr 2018 13:55:15 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 12 Apr 2018 09:05:59 +0200
x86/pti: Enable global pages for shared areas
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 <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/20180406205515.2977EE7D@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/mm/cpu_entry_area.c | 14 +++++++++++++-
arch/x86/mm/pti.c | 23 ++++++++++++++++++++++-
2 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 476d810639a8..b45f5aaefd74 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -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 --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 631507f0c198..8082f8b0c10e 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -299,6 +299,27 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
if (WARN_ON(!target_pmd))
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
@@ -348,7 +369,7 @@ static void __init pti_clone_entry_text(void)
{
pti_clone_pmds((unsigned long) __entry_text_start,
(unsigned long) __irqentry_text_end,
- _PAGE_RW | _PAGE_GLOBAL);
+ _PAGE_RW);
}
/*
--
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