[RFC PATCH 06/18] mm: introduce CONFIG_FREE_USER_PTE

From: Qi Zheng <zhengqi.arch@bytedance.com>
To: akpm@linux-foundation.org, tglx@linutronix.de,
	kirill.shutemov@linux.intel.com, mika.penttila@nextfour.com,
	david@redhat.com, jgg@nvidia.com, tj@kernel.org,
	dennis@kernel.org, ming.lei@redhat.com
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, songmuchun@bytedance.com,
	zhouchengming@bytedance.com,
	Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [RFC PATCH 06/18] mm: introduce CONFIG_FREE_USER_PTE
Date: Fri, 29 Apr 2022 21:35:40 +0800	[thread overview]
Message-ID: <20220429133552.33768-7-zhengqi.arch@bytedance.com> (raw)
In-Reply-To: <20220429133552.33768-1-zhengqi.arch@bytedance.com>

This configuration variable will be used to build the code needed to
free user PTE page table pages.

The PTE page table setting and clearing functions(such as set_pte_at())
are in the architecture's files, and these functions will be hooked to
implement FREE_USER_PTE, so the architecture support is needed.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/Kconfig | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 034d87953600..af99ed626732 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -909,6 +909,16 @@ config ANON_VMA_NAME
 	  area from being merged with adjacent virtual memory areas due to the
 	  difference in their name.
 
+config ARCH_SUPPORTS_FREE_USER_PTE
+	def_bool n
+
+config FREE_USER_PTE
+	bool "Free user PTE page tables"
+	default y
+	depends on ARCH_SUPPORTS_FREE_USER_PTE && MMU && SMP
+	help
+	  Try to free user PTE page table page when its all entries are none.
+
 source "mm/damon/Kconfig"
 
 endmenu
-- 
2.20.1

