On Tue, Sep 18, 2018 at 03:10:34PM +0100, Will Deacon wrote:
> So whilst I was reviewing this, I realised that I think we should be
> selecting HAVE_RCU_TABLE_INVALIDATE for arch/arm/ if HAVE_RCU_TABLE_FREE.
Yes very much so. Let me invert that option, you normally want that,
except if you don't natively use the linux page-tables.
---
Subject: asm-generic/tlb: Invert HAVE_RCU_TABLE_INVALIDATE
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed Sep 19 13:24:41 CEST 2018
Make issuing a TLB invalidate for page-table pages the normal case.
The reason is twofold:
- too many invalidates is safer than too few,
- most architectures use the linux page-tables natively
and would this require this.
Make it an opt-out, instead of an opt-in.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/Kconfig | 2 +-
arch/arm64/Kconfig | 1 -
arch/powerpc/Kconfig | 1 +
arch/sparc/Kconfig | 1 +
arch/x86/Kconfig | 1 -
include/asm-generic/tlb.h | 9 +++++----
mm/mmu_gather.c | 2 +-
7 files changed, 9 insertions(+), 8 deletions(-)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -362,7 +362,7 @@ config HAVE_ARCH_JUMP_LABEL
config HAVE_RCU_TABLE_FREE
bool
-config HAVE_RCU_TABLE_INVALIDATE
+config HAVE_RCU_TABLE_NO_INVALIDATE
bool
config HAVE_MMU_GATHER_PAGE_SIZE
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -142,7 +142,6 @@ config ARM64
select HAVE_PERF_USER_STACK_DUMP
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RCU_TABLE_FREE
- select HAVE_RCU_TABLE_INVALIDATE
select HAVE_RSEQ
select HAVE_STACKPROTECTOR
select HAVE_SYSCALL_TRACEPOINTS
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -216,6 +216,7 @@ config PPC
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_RCU_TABLE_FREE if SMP
+ select HAVE_RCU_TABLE_NO_INVALIDATE if HAVE_RCU_TABLE_FREE
select HAVE_MMU_GATHER_PAGE_SIZE
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE if PPC64 && CPU_LITTLE_ENDIAN
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -64,6 +64,7 @@ config SPARC64
select HAVE_KRETPROBES
select HAVE_KPROBES
select HAVE_RCU_TABLE_FREE if SMP
+ select HAVE_RCU_TABLE_NO_INVALIDATE if HAVE_RCU_TABLE_FREE
select HAVE_MEMBLOCK_NODE_MAP
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_DYNAMIC_FTRACE
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -181,7 +181,6 @@ config X86
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_RCU_TABLE_FREE if PARAVIRT
- select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -127,11 +127,12 @@
* When used, an architecture is expected to provide __tlb_remove_table()
* which does the actual freeing of these pages.
*
- * HAVE_RCU_TABLE_INVALIDATE
+ * HAVE_RCU_TABLE_NO_INVALIDATE
*
- * This makes HAVE_RCU_TABLE_FREE call tlb_flush_mmu_tlbonly() before freeing
- * the page-table pages. Required if you use HAVE_RCU_TABLE_FREE and your
- * architecture uses the Linux page-tables natively.
+ * This makes HAVE_RCU_TABLE_FREE avoid calling tlb_flush_mmu_tlbonly() before
+ * freeing the page-table pages. This can be avoided if you use
+ * HAVE_RCU_TABLE_FREE and your architecture does _NOT_ use the Linux
+ * page-tables natively.
*
*/
#define HAVE_GENERIC_MMU_GATHER
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -157,7 +157,7 @@ bool __tlb_remove_page_size(struct mmu_g
*/
static inline void tlb_table_invalidate(struct mmu_gather *tlb)
{
-#ifdef CONFIG_HAVE_RCU_TABLE_INVALIDATE
+#ifndef CONFIG_HAVE_RCU_TABLE_NO_INVALIDATE
/*
* Invalidate page-table caches used by hardware walkers. Then we still
* need to RCU-sched wait while freeing the pages because software
