[PATCH v4 1/8] mm, x86: Add HAVE_RCU_TABLE_FREE support

["Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>]

From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Implements optional HAVE_RCU_TABLE_FREE support for x86.

This is useful for things like Xen and KVM where paravirt tlb flush
means the software page table walkers like GUP-fast cannot rely on
IRQs disabling like regular x86 can.

Not for inclusion - is part of PeterZ's "Unify TLB gather implementations"
http://mid.gmane.org/20120627211540.459910855@chello.nl

Cc: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-r106wg6t7crxxhva55jnacrj@git.kernel.org
---
 arch/x86/include/asm/tlb.h |    1 +
 arch/x86/mm/pgtable.c      |    6 +++---
 include/asm-generic/tlb.h  |    9 +++++++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index 4fef207..f5489f0 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -1,6 +1,7 @@
 #ifndef _ASM_X86_TLB_H
 #define _ASM_X86_TLB_H
 
+#define __tlb_remove_table(table) free_page_and_swap_cache(table)
 #define tlb_start_vma(tlb, vma) do { } while (0)
 #define tlb_end_vma(tlb, vma) do { } while (0)
 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 8573b83..34fa168 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -51,21 +51,21 @@ void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
 {
 	pgtable_page_dtor(pte);
 	paravirt_release_pte(page_to_pfn(pte));
-	tlb_remove_page(tlb, pte);
+	tlb_remove_table(tlb, pte);
 }
 
 #if PAGETABLE_LEVELS > 2
 void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 {
 	paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
-	tlb_remove_page(tlb, virt_to_page(pmd));
+	tlb_remove_table(tlb, virt_to_page(pmd));
 }
 
 #if PAGETABLE_LEVELS > 3
 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
 {
 	paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
-	tlb_remove_page(tlb, virt_to_page(pud));
+	tlb_remove_table(tlb, virt_to_page(pud));
 }
 #endif	/* PAGETABLE_LEVELS > 3 */
 #endif	/* PAGETABLE_LEVELS > 2 */
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index ed6642a..d382b22 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -19,6 +19,8 @@
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 
+static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page);
+
 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
 /*
  * Semi RCU freeing of the page directories.
@@ -60,6 +62,13 @@ struct mmu_table_batch {
 extern void tlb_table_flush(struct mmu_gather *tlb);
 extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
 
+#else
+
+static inline void tlb_remove_table(struct mmu_gather *tlb, void *table)
+{
+	tlb_remove_page(tlb, table);
+}
+
 #endif
 
 /*