diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 5f18606125ff..2f1e44db42b6 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -121,11 +121,21 @@ extern pmdval_t early_pmd_flags;
  * The following only work if pte_present() is true.
  * Undefined behaviour if not..
  */
-static inline int pte_dirty(pte_t pte)
+static inline bool pte_dirty(pte_t pte)
 {
-	return pte_flags(pte) & _PAGE_DIRTY;
+	/*
+	 * A dirty PTE has Dirty=1 or Cow=1.
+	 */
+	return pte_flags(pte) & _PAGE_DIRTY_BITS;
 }
 
+static inline bool pte_shstk(pte_t pte)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return false;
+
+	return (pte_flags(pte) & (_PAGE_RW | _PAGE_DIRTY)) == _PAGE_DIRTY;
+}
 
 static inline u32 read_pkru(void)
 {
@@ -160,9 +170,20 @@ static inline int pte_young(pte_t pte)
 	return pte_flags(pte) & _PAGE_ACCESSED;
 }
 
-static inline int pmd_dirty(pmd_t pmd)
+static inline bool pmd_dirty(pmd_t pmd)
+{
+	/*
+	 * A dirty PMD has Dirty=1 or Cow=1.
+	 */
+	return pmd_flags(pmd) & _PAGE_DIRTY_BITS;
+}
+
+static inline bool pmd_shstk(pmd_t pmd)
 {
-	return pmd_flags(pmd) & _PAGE_DIRTY;
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return false;
+
+	return (pmd_flags(pmd) & (_PAGE_RW | _PAGE_DIRTY)) == _PAGE_DIRTY;
 }
 
 static inline int pmd_young(pmd_t pmd)
@@ -170,9 +191,12 @@ static inline int pmd_young(pmd_t pmd)
 	return pmd_flags(pmd) & _PAGE_ACCESSED;
 }
 
-static inline int pud_dirty(pud_t pud)
+static inline bool pud_dirty(pud_t pud)
 {
-	return pud_flags(pud) & _PAGE_DIRTY;
+	/*
+	 * A dirty PUD has Dirty=1 or Cow=1.
+	 */
+	return pud_flags(pud) & _PAGE_DIRTY_BITS;
 }
 
 static inline int pud_young(pud_t pud)
@@ -182,13 +206,23 @@ static inline int pud_young(pud_t pud)
 
 static inline int pte_write(pte_t pte)
 {
-	return pte_flags(pte) & _PAGE_RW;
+	/*
+	 * Shadow stack pages are always writable - but not by normal
+	 * instructions, and only by shadow stack operations.  Therefore,
+	 * the W=0,D=1 test with pte_shstk().
+	 */
+	return (pte_flags(pte) & _PAGE_RW) || pte_shstk(pte);
 }
 
 #define pmd_write pmd_write
 static inline int pmd_write(pmd_t pmd)
 {
-	return pmd_flags(pmd) & _PAGE_RW;
+	/*
+	 * Shadow stack pages are always writable - but not by normal
+	 * instructions, and only by shadow stack operations.  Therefore,
+	 * the W=0,D=1 test with pmd_shstk().
+	 */
+	return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
 }
 
 #define pud_write pud_write
@@ -326,6 +360,24 @@ static inline pte_t pte_clear_flags(pte_t pte, pteval_t clear)
 	return native_make_pte(v & ~clear);
 }
 
+static inline pte_t pte_mkcow(pte_t pte)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pte;
+
+	pte = pte_clear_flags(pte, _PAGE_DIRTY);
+	return pte_set_flags(pte, _PAGE_COW);
+}
+
+static inline pte_t pte_clear_cow(pte_t pte)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pte;
+
+	pte = pte_set_flags(pte, _PAGE_DIRTY);
+	return pte_clear_flags(pte, _PAGE_COW);
+}
+
 #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
 static inline int pte_uffd_wp(pte_t pte)
 {
@@ -345,7 +397,7 @@ static inline pte_t pte_clear_uffd_wp(pte_t pte)
 
 static inline pte_t pte_mkclean(pte_t pte)
 {
-	return pte_clear_flags(pte, _PAGE_DIRTY);
+	return pte_clear_flags(pte, _PAGE_DIRTY_BITS);
 }
 
 static inline pte_t pte_mkold(pte_t pte)
@@ -355,7 +407,16 @@ static inline pte_t pte_mkold(pte_t pte)
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
-	return pte_clear_flags(pte, _PAGE_RW);
+	pte = pte_clear_flags(pte, _PAGE_RW);
+
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PTE (RW=0, Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (pte_dirty(pte))
+		pte = pte_mkcow(pte);
+	return pte;
 }
 
 static inline pte_t pte_mkexec(pte_t pte)
@@ -365,7 +426,18 @@ static inline pte_t pte_mkexec(pte_t pte)
 
 static inline pte_t pte_mkdirty(pte_t pte)
 {
-	return pte_set_flags(pte, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+	pteval_t dirty = _PAGE_DIRTY;
+
+	/* Avoid creating (HW)Dirty=1, Write=0 PTEs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pte_write(pte))
+		dirty = _PAGE_COW;
+
+	return pte_set_flags(pte, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_mkwrite_shstk(pte_t pte)
+{
+	return pte_clear_cow(pte);
 }
 
 static inline pte_t pte_mkyoung(pte_t pte)
@@ -375,7 +447,12 @@ static inline pte_t pte_mkyoung(pte_t pte)
 
 static inline pte_t pte_mkwrite(pte_t pte)
 {
-	return pte_set_flags(pte, _PAGE_RW);
+	pte = pte_set_flags(pte, _PAGE_RW);
+
+	if (pte_dirty(pte))
+		pte = pte_clear_cow(pte);
+
+	return pte;
 }
 
 static inline pte_t pte_mkhuge(pte_t pte)
@@ -422,6 +499,24 @@ static inline pmd_t pmd_clear_flags(pmd_t pmd, pmdval_t clear)
 	return native_make_pmd(v & ~clear);
 }
 
+static inline pmd_t pmd_mkcow(pmd_t pmd)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pmd;
+
+	pmd = pmd_clear_flags(pmd, _PAGE_DIRTY);
+	return pmd_set_flags(pmd, _PAGE_COW);
+}
+
+static inline pmd_t pmd_clear_cow(pmd_t pmd)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pmd;
+
+	pmd = pmd_set_flags(pmd, _PAGE_DIRTY);
+	return pmd_clear_flags(pmd, _PAGE_COW);
+}
+
 #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
 static inline int pmd_uffd_wp(pmd_t pmd)
 {
@@ -446,17 +541,36 @@ static inline pmd_t pmd_mkold(pmd_t pmd)
 
 static inline pmd_t pmd_mkclean(pmd_t pmd)
 {
-	return pmd_clear_flags(pmd, _PAGE_DIRTY);
+	return pmd_clear_flags(pmd, _PAGE_DIRTY_BITS);
 }
 
 static inline pmd_t pmd_wrprotect(pmd_t pmd)
 {
-	return pmd_clear_flags(pmd, _PAGE_RW);
+	pmd = pmd_clear_flags(pmd, _PAGE_RW);
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PMD (RW=0, Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (pmd_dirty(pmd))
+		pmd = pmd_mkcow(pmd);
+	return pmd;
 }
 
 static inline pmd_t pmd_mkdirty(pmd_t pmd)
 {
-	return pmd_set_flags(pmd, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+	pmdval_t dirty = _PAGE_DIRTY;
+
+	/* Avoid creating (HW)Dirty=1, Write=0 PMDs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pmd_write(pmd))
+		dirty = _PAGE_COW;
+
+	return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pmd_t pmd_mkwrite_shstk(pmd_t pmd)
+{
+	return pmd_clear_cow(pmd);
 }
 
 static inline pmd_t pmd_mkdevmap(pmd_t pmd)
@@ -476,7 +590,11 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd)
 
 static inline pmd_t pmd_mkwrite(pmd_t pmd)
 {
-	return pmd_set_flags(pmd, _PAGE_RW);
+	pmd = pmd_set_flags(pmd, _PAGE_RW);
+
+	if (pmd_dirty(pmd))
+		pmd = pmd_clear_cow(pmd);
+	return pmd;
 }
 
 static inline pud_t pud_set_flags(pud_t pud, pudval_t set)
@@ -493,6 +611,24 @@ static inline pud_t pud_clear_flags(pud_t pud, pudval_t clear)
 	return native_make_pud(v & ~clear);
 }
 
+static inline pud_t pud_mkcow(pud_t pud)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pud;
+
+	pud = pud_clear_flags(pud, _PAGE_DIRTY);
+	return pud_set_flags(pud, _PAGE_COW);
+}
+
+static inline pud_t pud_clear_cow(pud_t pud)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pud;
+
+	pud = pud_set_flags(pud, _PAGE_DIRTY);
+	return pud_clear_flags(pud, _PAGE_COW);
+}
+
 static inline pud_t pud_mkold(pud_t pud)
 {
 	return pud_clear_flags(pud, _PAGE_ACCESSED);
@@ -500,17 +636,32 @@ static inline pud_t pud_mkold(pud_t pud)
 
 static inline pud_t pud_mkclean(pud_t pud)
 {
-	return pud_clear_flags(pud, _PAGE_DIRTY);
+	return pud_clear_flags(pud, _PAGE_DIRTY_BITS);
 }
 
 static inline pud_t pud_wrprotect(pud_t pud)
 {
-	return pud_clear_flags(pud, _PAGE_RW);
+	pud = pud_clear_flags(pud, _PAGE_RW);
+
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PUD (RW=0, Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (pud_dirty(pud))
+		pud = pud_mkcow(pud);
+	return pud;
 }
 
 static inline pud_t pud_mkdirty(pud_t pud)
 {
-	return pud_set_flags(pud, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+	pudval_t dirty = _PAGE_DIRTY;
+
+	/* Avoid creating (HW)Dirty=1, Write=0 PUDs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pud_write(pud))
+		dirty = _PAGE_COW;
+
+	return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY);
 }
 
 static inline pud_t pud_mkdevmap(pud_t pud)
@@ -530,7 +681,11 @@ static inline pud_t pud_mkyoung(pud_t pud)
 
 static inline pud_t pud_mkwrite(pud_t pud)
 {
-	return pud_set_flags(pud, _PAGE_RW);
+	pud = pud_set_flags(pud, _PAGE_RW);
+
+	if (pud_dirty(pud))
+		pud = pud_clear_cow(pud);
+	return pud;
 }
 
 #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 9db61817dfff..ce853c28c253 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -23,7 +23,8 @@
 #define _PAGE_BIT_SOFTW2	10	/* " */
 #define _PAGE_BIT_SOFTW3	11	/* " */
 #define _PAGE_BIT_PAT_LARGE	12	/* On 2MB or 1GB pages */
-#define _PAGE_BIT_SOFTW4	58	/* available for programmer */
+#define _PAGE_BIT_SOFTW4	57	/* available for programmer */
+#define _PAGE_BIT_SOFTW5	58	/* available for programmer */
 #define _PAGE_BIT_PKEY_BIT0	59	/* Protection Keys, bit 1/4 */
 #define _PAGE_BIT_PKEY_BIT1	60	/* Protection Keys, bit 2/4 */
 #define _PAGE_BIT_PKEY_BIT2	61	/* Protection Keys, bit 3/4 */
@@ -36,6 +37,15 @@
 #define _PAGE_BIT_SOFT_DIRTY	_PAGE_BIT_SOFTW3 /* software dirty tracking */
 #define _PAGE_BIT_DEVMAP	_PAGE_BIT_SOFTW4
 
+/*
+ * Indicates a copy-on-write page.
+ */
+#ifdef CONFIG_X86_SHADOW_STACK
+#define _PAGE_BIT_COW		_PAGE_BIT_SOFTW5 /* copy-on-write */
+#else
+#define _PAGE_BIT_COW		0
+#endif
+
 /* If _PAGE_BIT_PRESENT is clear, we use these: */
 /* - if the user mapped it with PROT_NONE; pte_present gives true */
 #define _PAGE_BIT_PROTNONE	_PAGE_BIT_GLOBAL
@@ -117,6 +127,36 @@
 #define _PAGE_DEVMAP	(_AT(pteval_t, 0))
 #endif
 
+/*
+ * The hardware requires shadow stack to be read-only and Dirty.
+ * _PAGE_COW is a software-only bit used to separate copy-on-write PTEs
+ * from shadow stack PTEs:
+ * (a) A modified, copy-on-write (COW) page: (Write=0, Cow=1)
+ * (b) A R/O page that has been COW'ed: (Write=0, Cow=1)
+ *     The user page is in a R/O VMA, and get_user_pages() needs a
+ *     writable copy.  The page fault handler creates a copy of the page
+ *     and sets the new copy's PTE as Write=0, Cow=1.
+ * (c) A shadow stack PTE: (Write=0, Dirty=1)
+ * (d) A shared (copy-on-access) shadow stack PTE: (Write=0, Cow=1)
+ *     When a shadow stack page is being shared among processes (this
+ *     happens at fork()), its PTE is cleared of _PAGE_DIRTY, so the next
+ *     shadow stack access causes a fault, and the page is duplicated and
+ *     _PAGE_DIRTY is set again.  This is the COW equivalent for shadow
+ *     stack pages, even though it's copy-on-access rather than
+ *     copy-on-write.
+ * (e) A page where the processor observed a Write=1 PTE, started a write,
+ *     set Dirty=1, but then observed a Write=0 PTE (changed by another
+ *     thread).  That's possible today, but will not happen on processors
+ *     that support shadow stack.
+ */
+#ifdef CONFIG_X86_SHADOW_STACK
+#define _PAGE_COW	(_AT(pteval_t, 1) << _PAGE_BIT_COW)
+#else
+#define _PAGE_COW	(_AT(pteval_t, 0))
+#endif
+
+#define _PAGE_DIRTY_BITS (_PAGE_DIRTY | _PAGE_COW)
+
 #define _PAGE_PROTNONE	(_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
 
 /*
