x86/mce/amd: Init thresholding machinery only on relevant vendors

... and not unconditionally.

 [ bp: Add a new vendor_flags bit for that. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200403161943.1458-3-bp@alien8.de

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

@@ -1442,15 +1442,20 @@ static void threshold_remove_bank(unsigned int cpu, int bank)
 
 int mce_threshold_remove_device(unsigned int cpu)
 {
+	struct threshold_bank **bp = this_cpu_read(threshold_banks);
 	unsigned int bank;
 
+	if (!bp)
+		return 0;
+
 	for (bank = 0; bank < per_cpu(mce_num_banks, cpu); ++bank) {
 		if (!(per_cpu(bank_map, cpu) & (1 << bank)))
 			continue;
 		threshold_remove_bank(cpu, bank);
 	}
-	kfree(per_cpu(threshold_banks, cpu));
-	per_cpu(threshold_banks, cpu) = NULL;
+	/* Clear the pointer before freeing the memory */
+	this_cpu_write(threshold_banks, NULL);
+	kfree(bp);
 	return 0;
 }
 
@@ -1461,6 +1466,9 @@ int mce_threshold_create_device(unsigned int cpu)
 	struct threshold_bank **bp;
 	int err = 0;
 
+	if (!mce_flags.amd_threshold)
+		return 0;
+
 	bp = per_cpu(threshold_banks, cpu);
 	if (bp)
 		return 0;

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

@@ -1756,6 +1756,7 @@ static void __mcheck_cpu_init_early(struct cpuinfo_x86 *c)
 		mce_flags.overflow_recov = !!cpu_has(c, X86_FEATURE_OVERFLOW_RECOV);
 		mce_flags.succor	 = !!cpu_has(c, X86_FEATURE_SUCCOR);
 		mce_flags.smca		 = !!cpu_has(c, X86_FEATURE_SMCA);
+		mce_flags.amd_threshold	 = 1;
 
 		if (mce_flags.smca) {
 			msr_ops.ctl	= smca_ctl_reg;

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

@@ -158,7 +158,10 @@ struct mce_vendor_flags {
 	 */
 	smca			: 1,
 
-	      __reserved_0	: 61;
+	/* AMD-style error thresholding banks present. */
+	amd_threshold		: 1,
+
+	__reserved_0		: 60;
 };
 
 extern struct mce_vendor_flags mce_flags;