[RFC PATCH 05/11] arm64: tlbflush: Allow stride to be specified for __flush_tlb_range()

Will Deacon
2018-08-24T15:52:41Z

When we are unmapping intermediate page-table entries or huge pages, we
don't need to issue a TLBI instruction for every PAGE_SIZE chunk in the
VA range being unmapped.

Allow the invalidation stride to be passed to __flush_tlb_range(), and
adjust our "just nuke the ASID" heuristic to take this into account.

Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm64/include/asm/tlb.h | 2 +-
arch/arm64/include/asm/tlbflush.h | 11 +++++++----
2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index a3233167be60..1e1f68ce28f4 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -53,7 +53,7 @@ static inline void tlb_flush(struct mmu_gather *tlb)
* the __(pte|pmd|pud)_free_tlb() functions, so last level
* TLBI is sufficient here.
*/
- __flush_tlb_range(&vma, tlb->start, tlb->end, true);
+ __flush_tlb_range(&vma, tlb->start, tlb->end, PAGE_SIZE, true);
}

static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index ddbf1718669d..1f77d08e638b 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -153,12 +153,15 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,

static inline void __flush_tlb_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end,
- bool last_level)
+ unsigned long stride, bool last_level)
{
unsigned long asid = ASID(vma->vm_mm);
unsigned long addr;

- if ((end - start) > MAX_TLB_RANGE) {
+ /* Convert the stride into units of 4k */
+ stride >>= 12;
+
+ if ((end - start) > (MAX_TLB_RANGE * stride)) {
flush_tlb_mm(vma->vm_mm);
return;
}
@@ -167,7 +170,7 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
end = __TLBI_VADDR(end, asid);

dsb(ishst);
- for (addr = start; addr < end; addr += 1 << (PAGE_SHIFT - 12)) {
+ for (addr = start; addr < end; addr += stride) {
if (last_level) {
__tlbi(vale1is, addr);
__tlbi_user(vale1is, addr);
@@ -186,7 +189,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
* We cannot use leaf-only invalidation here, since we may be invalidating
* table entries as part of collapsing hugepages or moving page tables.
*/
- __flush_tlb_range(vma, start, end, false);
+ __flush_tlb_range(vma, start, end, PAGE_SIZE, false);
}

static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end)
--
2.1.4