[PATCH v13 01/14] x86/mm: consolidate full flush threshold decision

Rik van Riel
2025-02-23T19:50:12Z

Reduce code duplication by consolidating the decision point
for whether to do individual invalidations or a full flush
inside get_flush_tlb_info.

Signed-off-by: Rik van Riel <riel@surriel.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
---
arch/x86/mm/tlb.c | 41 +++++++++++++++++++----------------------
1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index ffc25b348041..dbcb5c968ff9 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1000,6 +1000,15 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
#endif

+ /*
+ * If the number of flushes is so large that a full flush
+ * would be faster, do a full flush.
+ */
+ if ((end - start) >> stride_shift > tlb_single_page_flush_ceiling) {
+ start = 0;
+ end = TLB_FLUSH_ALL;
+ }
+
info->start = start;
info->end = end;
info->mm = mm;
@@ -1026,17 +1035,8 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
bool freed_tables)
{
struct flush_tlb_info *info;
+ int cpu = get_cpu();
u64 new_tlb_gen;
- int cpu;
-
- cpu = get_cpu();
-
- /* Should we flush just the requested range? */
- if ((end == TLB_FLUSH_ALL) ||
- ((end - start) >> stride_shift) > tlb_single_page_flush_ceiling) {
- start = 0;
- end = TLB_FLUSH_ALL;
- }

/* This is also a barrier that synchronizes with switch_mm(). */
new_tlb_gen = inc_mm_tlb_gen(mm);
@@ -1089,22 +1089,19 @@ static void do_kernel_range_flush(void *info)

void flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
- /* Balance as user space task's flush, a bit conservative */
- if (end == TLB_FLUSH_ALL ||
- (end - start) > tlb_single_page_flush_ceiling << PAGE_SHIFT) {
- on_each_cpu(do_flush_tlb_all, NULL, 1);
- } else {
- struct flush_tlb_info *info;
+ struct flush_tlb_info *info;
+
+ guard(preempt)();

- preempt_disable();
- info = get_flush_tlb_info(NULL, start, end, 0, false,
- TLB_GENERATION_INVALID);
+ info = get_flush_tlb_info(NULL, start, end, PAGE_SHIFT, false,
+ TLB_GENERATION_INVALID);

+ if (info->end == TLB_FLUSH_ALL)
+ on_each_cpu(do_flush_tlb_all, NULL, 1);
+ else
on_each_cpu(do_kernel_range_flush, info, 1);

- put_flush_tlb_info();
- preempt_enable();
- }
+ put_flush_tlb_info();
}

/*
--
2.47.1