x86/cpu: Read/save PPIN MSR during initialization

Currently, the PPIN (Protected Processor Inventory Number) MSR is read
by every CPU that processes a machine check, CMCI, or just polls machine
check banks from a periodic timer. This is not a "fast" MSR, so this
adds to overhead of processing errors.

Add a new "ppin" field to the cpuinfo_x86 structure. Read and save the
PPIN during initialization. Use this copy in mce_setup() instead of
reading the MSR.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220131230111.2004669-4-tony.luck@intel.com

Author: aegl

arch/x86/include/asm/processor.h

@@ -119,6 +119,8 @@ struct cpuinfo_x86 {
 	int			x86_cache_mbm_width_offset;
 	int			x86_power;
 	unsigned long		loops_per_jiffy;
+	/* protected processor identification number */
+	u64			ppin;
 	/* cpuid returned max cores value: */
 	u16			x86_max_cores;
 	u16			apicid;

arch/x86/kernel/cpu/common.c

@@ -91,14 +91,17 @@ DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_l2c_id) = BAD_APICID;
 static struct ppin_info {
 	int	feature;
 	int	msr_ppin_ctl;
+	int	msr_ppin;
 } ppin_info[] = {
 	[X86_VENDOR_INTEL] = {
 		.feature = X86_FEATURE_INTEL_PPIN,
 		.msr_ppin_ctl = MSR_PPIN_CTL,
+		.msr_ppin = MSR_PPIN
 	},
 	[X86_VENDOR_AMD] = {
 		.feature = X86_FEATURE_AMD_PPIN,
 		.msr_ppin_ctl = MSR_AMD_PPIN_CTL,
+		.msr_ppin = MSR_AMD_PPIN
 	},
 };
 
@@ -153,6 +156,7 @@ static void ppin_init(struct cpuinfo_x86 *c)
 
 	/* Is the enable bit set? */
 	if (val & 2UL) {
+		c->ppin = __rdmsr(info->msr_ppin);
 		set_cpu_cap(c, info->feature);
 		return;
 	}

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

@@ -138,12 +138,7 @@ void mce_setup(struct mce *m)
 	m->socketid = cpu_data(m->extcpu).phys_proc_id;
 	m->apicid = cpu_data(m->extcpu).initial_apicid;
 	m->mcgcap = __rdmsr(MSR_IA32_MCG_CAP);
-
-	if (this_cpu_has(X86_FEATURE_INTEL_PPIN))
-		m->ppin = __rdmsr(MSR_PPIN);
-	else if (this_cpu_has(X86_FEATURE_AMD_PPIN))
-		m->ppin = __rdmsr(MSR_AMD_PPIN);
-
+	m->ppin = cpu_data(m->extcpu).ppin;
 	m->microcode = boot_cpu_data.microcode;
 }