Merge commit 'its-for-linus-20250509-merge' into x86/core, to resolve conflicts

 Conflicts:
	Documentation/admin-guide/hw-vuln/index.rst
	arch/x86/include/asm/cpufeatures.h
	arch/x86/kernel/alternative.c
	arch/x86/kernel/cpu/bugs.c
	arch/x86/kernel/cpu/common.c
	drivers/base/cpu.c
	include/linux/cpu.h

Signed-off-by: Ingo Molnar <mingo@kernel.org>

4 files changed, 53 insertions, 0 deletions

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index e18cdaa1573c..15bc07a5ebb3 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -6,6 +6,7 @@
 #include <linux/stringify.h>
 #include <linux/objtool.h>
 #include <asm/asm.h>
+#include <asm/bug.h>
 
 #define ALT_FLAGS_SHIFT		16
 
@@ -130,6 +131,37 @@ static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
 }
 #endif
 
+#ifdef CONFIG_MITIGATION_ITS
+extern void its_init_mod(struct module *mod);
+extern void its_fini_mod(struct module *mod);
+extern void its_free_mod(struct module *mod);
+extern u8 *its_static_thunk(int reg);
+#else /* CONFIG_MITIGATION_ITS */
+static inline void its_init_mod(struct module *mod) { }
+static inline void its_fini_mod(struct module *mod) { }
+static inline void its_free_mod(struct module *mod) { }
+static inline u8 *its_static_thunk(int reg)
+{
+	WARN_ONCE(1, "ITS not compiled in");
+
+	return NULL;
+}
+#endif
+
+#if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL)
+extern bool cpu_wants_rethunk(void);
+extern bool cpu_wants_rethunk_at(void *addr);
+#else
+static __always_inline bool cpu_wants_rethunk(void)
+{
+	return false;
+}
+static __always_inline bool cpu_wants_rethunk_at(void *addr)
+{
+	return false;
+}
+#endif
+
 #ifdef CONFIG_SMP
 extern void alternatives_smp_module_add(struct module *mod, char *name,
 					void *locks, void *locks_end,
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 7642310276a8..f67a93fc9391 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -482,6 +482,7 @@
 #define X86_FEATURE_AMD_WORKLOAD_CLASS	(21*32+ 7) /* Workload Classification */
 #define X86_FEATURE_PREFER_YMM		(21*32+ 8) /* Avoid ZMM registers due to downclocking */
 #define X86_FEATURE_APX			(21*32+ 9) /* Advanced Performance Extensions */
+#define X86_FEATURE_INDIRECT_THUNK_ITS	(21*32+10) /* Use thunk for indirect branches in lower half of cacheline */
 
 /*
  * BUG word(s)
@@ -535,5 +536,7 @@
 #define X86_BUG_IBPB_NO_RET		X86_BUG( 1*32+ 4) /* "ibpb_no_ret" IBPB omits return target predictions */
 #define X86_BUG_SPECTRE_V2_USER		X86_BUG( 1*32+ 5) /* "spectre_v2_user" CPU is affected by Spectre variant 2 attack between user processes */
 #define X86_BUG_OLD_MICROCODE		X86_BUG( 1*32+ 6) /* "old_microcode" CPU has old microcode, it is surely vulnerable to something */
+#define X86_BUG_ITS			X86_BUG( 1*32+ 7) /* "its" CPU is affected by Indirect Target Selection */
+#define X86_BUG_ITS_NATIVE_ONLY		X86_BUG( 1*32+ 8) /* "its_native_only" CPU is affected by ITS, VMX is not affected */
 
 #endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index e0d60805b869..c6143bd7db58 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -211,6 +211,14 @@
 						 * VERW clears CPU Register
 						 * File.
 						 */
+#define ARCH_CAP_ITS_NO			BIT_ULL(62) /*
+						     * Not susceptible to
+						     * Indirect Target Selection.
+						     * This bit is not set by
+						     * HW, but is synthesized by
+						     * VMMs for guests to know
+						     * their affected status.
+						     */
 
 #define MSR_IA32_FLUSH_CMD		0x0000010b
 #define L1D_FLUSH			BIT(0)	/*
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51a677fe9a8d..20d754b98f3f 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -336,10 +336,14 @@
 
 #else /* __ASSEMBLER__ */
 
+#define ITS_THUNK_SIZE	64
+
 typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
+typedef u8 its_thunk_t[ITS_THUNK_SIZE];
 extern retpoline_thunk_t __x86_indirect_thunk_array[];
 extern retpoline_thunk_t __x86_indirect_call_thunk_array[];
 extern retpoline_thunk_t __x86_indirect_jump_thunk_array[];
+extern its_thunk_t	 __x86_indirect_its_thunk_array[];
 
 #ifdef CONFIG_MITIGATION_RETHUNK
 extern void __x86_return_thunk(void);
@@ -363,6 +367,12 @@ static inline void srso_return_thunk(void) {}
 static inline void srso_alias_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_MITIGATION_ITS
+extern void its_return_thunk(void);
+#else
+static inline void its_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);