Merge tag 'x86-urgent-2024-06-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
 "Miscellaneous fixes:

   - Fix kexec() crash if call depth tracking is enabled

   - Fix SMN reads on inaccessible registers on certain AMD systems"

* tag 'x86-urgent-2024-06-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/amd_nb: Check for invalid SMN reads
  x86/kexec: Fix bug with call depth tracking

arch/x86/kernel/amd_nb.c

@@ -215,7 +215,14 @@ static int __amd_smn_rw(u16 node, u32 address, u32 *value, bool write)
 
 int amd_smn_read(u16 node, u32 address, u32 *value)
 {
-	return __amd_smn_rw(node, address, value, false);
+	int err = __amd_smn_rw(node, address, value, false);
+
+	if (PCI_POSSIBLE_ERROR(*value)) {
+		err = -ENODEV;
+		*value = 0;
+	}
+
+	return err;
 }
 EXPORT_SYMBOL_GPL(amd_smn_read);
 

arch/x86/kernel/machine_kexec_64.c

@@ -295,8 +295,15 @@ void machine_kexec_cleanup(struct kimage *image)
 void machine_kexec(struct kimage *image)
 {
 	unsigned long page_list[PAGES_NR];
-	void *control_page;
+	unsigned int host_mem_enc_active;
 	int save_ftrace_enabled;
+	void *control_page;
+
+	/*
+	 * This must be done before load_segments() since if call depth tracking
+	 * is used then GS must be valid to make any function calls.
+	 */
+	host_mem_enc_active = cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT);
 
 #ifdef CONFIG_KEXEC_JUMP
 	if (image->preserve_context)
@@ -358,7 +365,7 @@ void machine_kexec(struct kimage *image)
 				       (unsigned long)page_list,
 				       image->start,
 				       image->preserve_context,
-				       cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT));
+				       host_mem_enc_active);
 
 #ifdef CONFIG_KEXEC_JUMP
 	if (image->preserve_context)