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authorZachary Amsden <zach@vmware.com>2006-09-30 23:29:36 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-01 00:39:34 -0700
commitd6d861e3c963b4077c83e078e3e300c4b81f93e7 (patch)
tree842071ac905575aa0ea8bedd3a1ac5db29416bcf
parent23002d88be309a7c78db69363c9d933a29a3b0bb (diff)
[PATCH] paravirt: optimize ptep establish for pae
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@vmware.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/asm-i386/pgtable-2level.h1
-rw-r--r--include/asm-i386/pgtable-3level.h15
-rw-r--r--include/asm-i386/pgtable.h11
3 files changed, 27 insertions, 0 deletions
diff --git a/include/asm-i386/pgtable-2level.h b/include/asm-i386/pgtable-2level.h
index 201c86a6711..8d8d3b9ecdb 100644
--- a/include/asm-i386/pgtable-2level.h
+++ b/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 --git a/include/asm-i386/pgtable-3level.h b/include/asm-i386/pgtable-3level.h
index 0d899173232..7c58debdb39 100644
--- a/include/asm-i386/pgtable-3level.h
+++ b/include/asm-i386/pgtable-3level.h
@@ -58,6 +58,21 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
}
#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 --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index ee9696d2f67..8cb708a6bed 100644
--- a/include/asm-i386/pgtable.h
+++ b/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) \
({ \