The patch titled
paravirt: optimize ptep establish for pae
has been added to the -mm tree. Its filename is
paravirt-optimize-ptep-establish-for-pae.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: paravirt: optimize ptep establish for pae
From: Zachary Amsden <zach@xxxxxxxxxx>
The ptep_establish macro is only used on user-level PTEs, for P->P mapping
changes. Since these always happen under protection of the pagetable lock,
the strong synchronization of a 64-bit cmpxchg is not needed, in fact, not
even a lock prefix needs to be used. We can simply instead clear the P-bit,
followed by a normal set. The write ordering is still important to avoid the
possibility of the TLB snooping a partially written PTE and getting a bad
mapping installed.
Signed-off-by: Zachary Amsden <zach@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/asm-i386/pgtable-2level.h | 1 +
include/asm-i386/pgtable-3level.h | 15 +++++++++++++++
include/asm-i386/pgtable.h | 11 +++++++++++
3 files changed, 27 insertions(+)
diff -puN include/asm-i386/pgtable-2level.h~paravirt-optimize-ptep-establish-for-pae include/asm-i386/pgtable-2level.h
--- a/include/asm-i386/pgtable-2level.h~paravirt-optimize-ptep-establish-for-pae
+++ a/include/asm-i386/pgtable-2level.h
@@ -16,6 +16,7 @@
#define set_pte(pteptr, pteval) (*(pteptr) = pteval)
#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
#define set_pte_atomic(pteptr, pteval) set_pte(pteptr,pteval)
+#define set_pte_present(mm,addr,ptep,pteval) set_pte_at(mm,addr,ptep,pteval)
#define set_pmd(pmdptr, pmdval) (*(pmdptr) = (pmdval))
#define pte_clear(mm,addr,xp) do { set_pte_at(mm, addr, xp, __pte(0)); } while (0)
diff -puN include/asm-i386/pgtable-3level.h~paravirt-optimize-ptep-establish-for-pae include/asm-i386/pgtable-3level.h
--- a/include/asm-i386/pgtable-3level.h~paravirt-optimize-ptep-establish-for-pae
+++ a/include/asm-i386/pgtable-3level.h
@@ -58,6 +58,21 @@ static inline void set_pte(pte_t *ptep,
}
#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
+/*
+ * Since this is only called on user PTEs, and the page fault handler
+ * must handle the already racy situation of simultaneous page faults,
+ * we are justified in merely clearing the PTE present bit, followed
+ * by a set. The ordering here is important.
+ */
+static inline void set_pte_present(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte)
+{
+ ptep->pte_low = 0;
+ smp_wmb();
+ ptep->pte_high = pte.pte_high;
+ smp_wmb();
+ ptep->pte_low = pte.pte_low;
+}
+
#define __HAVE_ARCH_SET_PTE_ATOMIC
#define set_pte_atomic(pteptr,pteval) \
set_64bit((unsigned long long *)(pteptr),pte_val(pteval))
diff -puN include/asm-i386/pgtable.h~paravirt-optimize-ptep-establish-for-pae include/asm-i386/pgtable.h
--- a/include/asm-i386/pgtable.h~paravirt-optimize-ptep-establish-for-pae
+++ a/include/asm-i386/pgtable.h
@@ -269,6 +269,17 @@ do { \
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
+/*
+ * Rules for using ptep_establish: the pte MUST be a user pte, and
+ * must be a present->present transition.
+ */
+#define __HAVE_ARCH_PTEP_ESTABLISH
+#define ptep_establish(vma, address, ptep, pteval) \
+do { \
+ set_pte_present((vma)->vm_mm, address, ptep, pteval); \
+ flush_tlb_page(vma, address); \
+} while (0)
+
#define __HAVE_ARCH_PTEP_CLEAR_DIRTY_FLUSH
#define ptep_clear_flush_dirty(vma, address, ptep) \
({ \
_
Patches currently in -mm which might be from zach@xxxxxxxxxx are
split-i386-and-x86_64-ptraceh.patch
uml-use-ptrace-abih-instead-of-ptraceh.patch
x86-allow-a-kernel-to-not-be-in-ring-0.patch
x86-allow-a-kernel-to-not-be-in-ring-0-tidy.patch
x86-add-a-bootparameter-to-reserve-high-linear-address-space.patch
x86-trivial-pgtableh-__assembly__-move.patch
x86-trivial-move-of-__have-macros-in-i386-pagetable-headers.patch
x86-trivial-move-of-ptep_set_access_flags.patch
x86-remove-unused-include-from-efi_stubs.patch
paravirt-remove-read-hazard-from-cow.patch
paravirt-pte-clear-not-present.patch
paravirt-lazy-mmu-mode-hooks.patch
paravirt-combine-flush-accessed-dirty.patch
paravirt-kpte-flush.patch
paravirt-optimize-ptep-establish-for-pae.patch
paravirt-remove-set-pte-atomic.patch
paravirt-pae-compile-fix.patch
paravirt-update-pte-hook.patch
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