[PATCH v4 14/23] x86/mm/cpa: Add set_direct_map_ functions

[Rick Edgecombe]

Add two new functions set_direct_map_default_noflush() and
set_direct_map_invalid_noflush() for setting the direct map alias for the
page to its default valid permissions and to an invalid state that cannot
be cached in a TLB, respectively. These functions do not flush the TLB.

Note, __kernel_map_pages() does something similar but flushes the TLB and
doesn't reset the permission bits to default on all architectures.

Also add an ARCH config ARCH_HAS_SET_DIRECT_MAP for specifying whether
these have an actual implementation or a default empty one.

Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
 arch/Kconfig                      |  4 ++++
 arch/x86/Kconfig                  |  1 +
 arch/x86/include/asm/set_memory.h |  3 +++
 arch/x86/mm/pageattr.c            | 14 +++++++++++---
 include/linux/set_memory.h        | 11 +++++++++++
 5 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 3ab446bd12ef..5e43fcbad4ca 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -249,6 +249,10 @@ config ARCH_HAS_FORTIFY_SOURCE
 config ARCH_HAS_SET_MEMORY
 	bool
 
+# Select if arch has all set_direct_map_invalid/default() functions
+config ARCH_HAS_SET_DIRECT_MAP
+	bool
+
 # Select if arch init_task must go in the __init_task_data section
 config ARCH_TASK_STRUCT_ON_STACK
        bool
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2ec5e850b807..45d788354376 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -66,6 +66,7 @@ config X86
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
 	select ARCH_HAS_UACCESS_MCSAFE		if X86_64 && X86_MCE
 	select ARCH_HAS_SET_MEMORY
+	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 07a25753e85c..ae7b909dc242 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -85,6 +85,9 @@ int set_pages_nx(struct page *page, int numpages);
 int set_pages_ro(struct page *page, int numpages);
 int set_pages_rw(struct page *page, int numpages);
 
+int set_direct_map_invalid_noflush(struct page *page);
+int set_direct_map_default_noflush(struct page *page);
+
 extern int kernel_set_to_readonly;
 void set_kernel_text_rw(void);
 void set_kernel_text_ro(void);
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 4c570612e24e..3574550192c6 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -2209,8 +2209,6 @@ int set_pages_rw(struct page *page, int numpages)
 	return set_memory_rw(addr, numpages);
 }
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
-
 static int __set_pages_p(struct page *page, int numpages)
 {
 	unsigned long tempaddr = (unsigned long) page_address(page);
@@ -2249,6 +2247,17 @@ static int __set_pages_np(struct page *page, int numpages)
 	return __change_page_attr_set_clr(&cpa, 0);
 }
 
+int set_direct_map_invalid_noflush(struct page *page)
+{
+	return __set_pages_np(page, 1);
+}
+
+int set_direct_map_default_noflush(struct page *page)
+{
+	return __set_pages_p(page, 1);
+}
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	if (PageHighMem(page))
@@ -2282,7 +2291,6 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
 }
 
 #ifdef CONFIG_HIBERNATION
-
 bool kernel_page_present(struct page *page)
 {
 	unsigned int level;
diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index 2a986d282a97..b5071497b8cb 100644
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -17,6 +17,17 @@ static inline int set_memory_x(unsigned long addr,  int numpages) { return 0; }
 static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
 #endif
 
+#ifndef CONFIG_ARCH_HAS_SET_DIRECT_MAP
+static inline int set_direct_map_invalid_noflush(struct page *page)
+{
+	return 0;
+}
+static inline int set_direct_map_default_noflush(struct page *page)
+{
+	return 0;
+}
+#endif
+
 #ifndef set_mce_nospec
 static inline int set_mce_nospec(unsigned long pfn)
 {
-- 
2.17.1