[RFC PATCH 08/11] asm-generic/tlb: Track freeing of page-table directories in struct mmu_gather

[Will Deacon]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Some architectures require different TLB invalidation instructions
depending on whether it is only the last-level of page table being
changed, or whether there are also changes to the intermediate
(directory) entries higher up the tree.

Add a new bit to the flags bitfield in struct mmu_gather so that the
architecture code can operate accordingly if it's the intermediate
levels being invalidated.

Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
 include/asm-generic/tlb.h | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 859f897d3d53..a5caf90264e6 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -99,12 +99,22 @@ struct mmu_gather {
 #endif
 	unsigned long		start;
 	unsigned long		end;
-	/* we are in the middle of an operation to clear
-	 * a full mm and can make some optimizations */
-	unsigned int		fullmm : 1,
-	/* we have performed an operation which
-	 * requires a complete flush of the tlb */
-				need_flush_all : 1;
+	/*
+	 * we are in the middle of an operation to clear
+	 * a full mm and can make some optimizations
+	 */
+	unsigned int		fullmm : 1;
+
+	/*
+	 * we have performed an operation which
+	 * requires a complete flush of the tlb
+	 */
+	unsigned int		need_flush_all : 1;
+
+	/*
+	 * we have removed page directories
+	 */
+	unsigned int		freed_tables : 1;
 
 	struct mmu_gather_batch *active;
 	struct mmu_gather_batch	local;
@@ -139,6 +149,7 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
 		tlb->start = TASK_SIZE;
 		tlb->end = 0;
 	}
+	tlb->freed_tables = 0;
 }
 
 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
@@ -280,6 +291,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define pte_free_tlb(tlb, ptep, address)			\
 	do {							\
 		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\
+		tlb->freed_tables = 1;			\
 		__pte_free_tlb(tlb, ptep, address);		\
 	} while (0)
 #endif
@@ -287,7 +299,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #ifndef pmd_free_tlb
 #define pmd_free_tlb(tlb, pmdp, address)			\
 	do {							\
-		__tlb_adjust_range(tlb, address, PAGE_SIZE);		\
+		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\
+		tlb->freed_tables = 1;			\
 		__pmd_free_tlb(tlb, pmdp, address);		\
 	} while (0)
 #endif
@@ -297,6 +310,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #define pud_free_tlb(tlb, pudp, address)			\
 	do {							\
 		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\
+		tlb->freed_tables = 1;			\
 		__pud_free_tlb(tlb, pudp, address);		\
 	} while (0)
 #endif
@@ -306,7 +320,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 #ifndef p4d_free_tlb
 #define p4d_free_tlb(tlb, pudp, address)			\
 	do {							\
-		__tlb_adjust_range(tlb, address, PAGE_SIZE);		\
+		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\
+		tlb->freed_tables = 1;			\
 		__p4d_free_tlb(tlb, pudp, address);		\
 	} while (0)
 #endif
-- 
2.1.4