Merge tag 'x86_microcode_for_v7.0_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 microcode loader update from Borislav Petkov:

 - Since debugging the microcode loader makes sense on baremetal too (it
   was used in a guest only until now), extend it to be able to do that
   too

* tag 'x86_microcode_for_v7.0_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/microcode/AMD: Allow loader debugging to be enabled on baremetal too

Author: torvalds

arch/x86/Kconfig

@@ -1380,10 +1380,12 @@ config MICROCODE_DBG
 	default n
 	depends on MICROCODE
 	help
-	  Enable code which allows for debugging the microcode loader in
-	  a guest. Meaning the patch loading is simulated but everything else
+	  Enable code which allows to debug the microcode loader. When running
+	  in a guest the patch loading is simulated but everything else
 	  related to patch parsing and handling is done as on baremetal with
-	  the purpose of debugging solely the software side of things.
+	  the purpose of debugging solely the software side of things. On
+	  baremetal, it simply dumps additional debugging information during
+	  normal operation.
 
 	  You almost certainly want to say n here.
 

arch/x86/kernel/cpu/microcode/amd.c

@@ -322,7 +322,7 @@ static u32 get_patch_level(void)
 {
 	u32 rev, dummy __always_unused;
 
-	if (IS_ENABLED(CONFIG_MICROCODE_DBG)) {
+	if (IS_ENABLED(CONFIG_MICROCODE_DBG) && hypervisor_present) {
 		int cpu = smp_processor_id();
 
 		if (!microcode_rev[cpu]) {
@@ -714,7 +714,7 @@ static bool __apply_microcode_amd(struct microcode_amd *mc, u32 *cur_rev,
 			invlpg(p_addr_end);
 	}
 
-	if (IS_ENABLED(CONFIG_MICROCODE_DBG))
+	if (IS_ENABLED(CONFIG_MICROCODE_DBG) && hypervisor_present)
 		microcode_rev[smp_processor_id()] = mc->hdr.patch_id;
 
 	/* verify patch application was successful */

arch/x86/kernel/cpu/microcode/core.c

@@ -57,6 +57,8 @@ bool force_minrev = IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV);
 u32 base_rev;
 u32 microcode_rev[NR_CPUS] = {};
 
+bool hypervisor_present;
+
 /*
  * Synchronization.
  *
@@ -117,7 +119,13 @@ bool __init microcode_loader_disabled(void)
 	 * Disable when:
 	 *
 	 * 1) The CPU does not support CPUID.
-	 *
+	 */
+	if (!cpuid_feature()) {
+		dis_ucode_ldr = true;
+		return dis_ucode_ldr;
+	}
+
+	/*
 	 * 2) Bit 31 in CPUID[1]:ECX is clear
 	 *    The bit is reserved for hypervisor use. This is still not
 	 *    completely accurate as XEN PV guests don't see that CPUID bit
@@ -127,9 +135,9 @@ bool __init microcode_loader_disabled(void)
 	 * 3) Certain AMD patch levels are not allowed to be
 	 *    overwritten.
 	 */
-	if (!cpuid_feature() ||
-	    ((native_cpuid_ecx(1) & BIT(31)) &&
-	      !IS_ENABLED(CONFIG_MICROCODE_DBG)) ||
+	hypervisor_present = native_cpuid_ecx(1) & BIT(31);
+
+	if ((hypervisor_present && !IS_ENABLED(CONFIG_MICROCODE_DBG)) ||
 	    amd_check_current_patch_level())
 		dis_ucode_ldr = true;
 

arch/x86/kernel/cpu/microcode/internal.h

@@ -48,6 +48,7 @@ extern struct early_load_data early_data;
 extern struct ucode_cpu_info ucode_cpu_info[];
 extern u32 microcode_rev[NR_CPUS];
 extern u32 base_rev;
+extern bool hypervisor_present;
 
 struct cpio_data find_microcode_in_initrd(const char *path);