Hi Barry，
On 2022/7/11 11:46, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>
Platforms like ARM64 have hareware TLB shootdown broadcast. They
don't maintain mm_cpumask but just send tlbi and related sync
instructions for TLB flush. task's mm_cpumask is normally empty
in this case. We also allow deferred TLB flush on this kind of
platforms.
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>>
---
...
diff --git a/mm/Kconfig b/mm/Kconfig
index 169e64192e48..7bf54f57ca01 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -951,6 +951,9 @@ config ARCH_HAS_CURRENT_STACK_POINTER
register alias named "current_stack_pointer", this config can be
selected.
+config ARCH_HAS_MM_CPUMASK
+ bool
+
config ARCH_HAS_VM_GET_PAGE_PROT
bool
diff --git a/mm/rmap.c b/mm/rmap.c
index 5bcb334cd6f2..13d4f9a1d4f1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -692,6 +692,10 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
if (!(flags & TTU_BATCH_FLUSH))
return false;
+#ifndef CONFIG_ARCH_HAS_MM_CPUMASK
+ return true;
+#endif
+
Here is another option to enable arch's tlbbatch defer
[1]
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20171101101735.2318-2-khandual@xxxxxxxxxxxxxxxxxx/
/* If remote CPUs need to be flushed then defer batch the flush */
if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
should_defer = true;
