[PATCH v1 08/13] arm64: mm: Simplify __flush_tlb_range_limit_excess()

Ryan Roberts
2025-12-16T14:46:25Z

From: Will Deacon <will@kernel.org>

__flush_tlb_range_limit_excess() is unnecessarily complicated:

- It takes a 'start', 'end' and 'pages' argument, whereas it only
needs 'pages' (which the caller has computed from the other two
arguments!).

- It erroneously compares 'pages' with MAX_TLBI_RANGE_PAGES when
the system doesn't support range-based invalidation but the range to
be invalidated would result in fewer than MAX_DVM_OPS invalidations.

Simplify the function so that it no longer takes the 'start' and 'end'
arguments and only considers the MAX_TLBI_RANGE_PAGES threshold on
systems that implement range-based invalidation.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---
arch/arm64/include/asm/tlbflush.h | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index 0e1902f66e01..3b72a71feac0 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -527,21 +527,13 @@ static __always_inline void __flush_tlb_range_op(tlbi_op lop, tlbi_op rop,
#define __flush_s2_tlb_range_op(op, start, pages, stride, tlb_level) \
__flush_tlb_range_op(op, r##op, start, pages, stride, 0, tlb_level, kvm_lpa2_is_enabled())

-static inline bool __flush_tlb_range_limit_excess(unsigned long start,
- unsigned long end, unsigned long pages, unsigned long stride)
+static inline bool __flush_tlb_range_limit_excess(unsigned long pages,
+ unsigned long stride)
{
- /*
- * When the system does not support TLB range based flush
- * operation, (MAX_DVM_OPS - 1) pages can be handled. But
- * with TLB range based operation, MAX_TLBI_RANGE_PAGES
- * pages can be handled.
- */
- if ((!system_supports_tlb_range() &&
- (end - start) >= (MAX_DVM_OPS * stride)) ||
- pages > MAX_TLBI_RANGE_PAGES)
+ if (system_supports_tlb_range() && pages > MAX_TLBI_RANGE_PAGES)
return true;

- return false;
+ return pages >= (MAX_DVM_OPS * stride) >> PAGE_SHIFT;
}

static inline void __flush_tlb_range_nosync(struct mm_struct *mm,
@@ -555,7 +547,7 @@ static inline void __flush_tlb_range_nosync(struct mm_struct *mm,
end = round_up(end, stride);
pages = (end - start) >> PAGE_SHIFT;

- if (__flush_tlb_range_limit_excess(start, end, pages, stride)) {
+ if (__flush_tlb_range_limit_excess(pages, stride)) {
flush_tlb_mm(mm);
return;
}
@@ -619,7 +611,7 @@ static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end
end = round_up(end, stride);
pages = (end - start) >> PAGE_SHIFT;

- if (__flush_tlb_range_limit_excess(start, end, pages, stride)) {
+ if (__flush_tlb_range_limit_excess(pages, stride)) {
flush_tlb_all();
return;
}
--
2.43.0