[PATCH v7 3/3] x86/mm: add set_direct_map_ro()

[Xueyuan Chen]

Implement set_direct_map_ro() for x86 with a page-based interface. Clear
_PAGE_RW and _PAGE_DIRTY through the CPA path and let the common CPA
wrapper invalidate stale writable translations before returning.

Co-developed-by: Lance Yang <lance.yang at linux.dev>
Signed-off-by: Lance Yang <lance.yang at linux.dev>
Signed-off-by: Xueyuan Chen <xueyuan.chen21 at gmail.com>
---
 arch/x86/include/asm/set_memory.h |  2 ++
 arch/x86/mm/pat/set_memory.c      | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 39271a5ea925..710164ea8258 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -88,6 +88,8 @@ int set_pages_rw(struct page *page, int numpages);
 
 int set_direct_map_invalid_noflush(struct page *page, unsigned int nr);
 int set_direct_map_default_noflush(struct page *page, unsigned int nr);
+int set_direct_map_ro(struct page *page, unsigned int nr);
+#define set_direct_map_ro set_direct_map_ro
 bool kernel_page_present(struct page *page);
 
 extern int kernel_set_to_readonly;
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index a1a061d995b3..7c0cfa7acd17 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2666,6 +2666,16 @@ int set_direct_map_default_noflush(struct page *page, unsigned int nr)
 	return __set_pages_p(page, nr, 0);
 }
 
+int set_direct_map_ro(struct page *page, unsigned int nr)
+{
+	unsigned long addr = (unsigned long)page_address(page);
+
+	/* Direct-map callers are expected to pass pages without aliases. */
+	return change_page_attr_set_clr(&addr, nr, __pgprot(0),
+					__pgprot(_PAGE_RW | _PAGE_DIRTY), 0,
+					CPA_NO_CHECK_ALIAS, NULL);
+}
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
-- 
2.47.3