x86/MCE: Export memory_error()

Export the function which checks whether an MCE is a memory error to
other users so that we can reuse the logic. Drop the boot_cpu_data use,
while at it, as mce.cpuvendor already has the CPU vendor in there.

Integrate a piece from a patch from Vishal Verma
<vishal.l.verma@intel.com> to export it for modules (nfit).

The main reason we're exporting it is that the nfit handler
nfit_handle_mce() needs to detect a memory error properly before doing
its recovery actions.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170519093915.15413-2-bp@alien8.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/mce.h

@@ -266,6 +266,7 @@ static inline int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *s
 #endif
 
 int mce_available(struct cpuinfo_x86 *c);
+bool mce_is_memory_error(struct mce *m);
 
 DECLARE_PER_CPU(unsigned, mce_exception_count);
 DECLARE_PER_CPU(unsigned, mce_poll_count);

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

@@ -499,16 +499,14 @@ static int mce_usable_address(struct mce *m)
 	return 1;
 }
 
-static bool memory_error(struct mce *m)
+bool mce_is_memory_error(struct mce *m)
 {
-	struct cpuinfo_x86 *c = &boot_cpu_data;
-
-	if (c->x86_vendor == X86_VENDOR_AMD) {
+	if (m->cpuvendor == X86_VENDOR_AMD) {
 		/* ErrCodeExt[20:16] */
 		u8 xec = (m->status >> 16) & 0x1f;
 
 		return (xec == 0x0 || xec == 0x8);
-	} else if (c->x86_vendor == X86_VENDOR_INTEL) {
+	} else if (m->cpuvendor == X86_VENDOR_INTEL) {
 		/*
 		 * Intel SDM Volume 3B - 15.9.2 Compound Error Codes
 		 *
@@ -529,6 +527,7 @@ static bool memory_error(struct mce *m)
 
 	return false;
 }
+EXPORT_SYMBOL_GPL(mce_is_memory_error);
 
 static bool cec_add_mce(struct mce *m)
 {
@@ -536,7 +535,7 @@ static bool cec_add_mce(struct mce *m)
 		return false;
 
 	/* We eat only correctable DRAM errors with usable addresses. */
-	if (memory_error(m) &&
+	if (mce_is_memory_error(m) &&
 	    !(m->status & MCI_STATUS_UC) &&
 	    mce_usable_address(m))
 		if (!cec_add_elem(m->addr >> PAGE_SHIFT))
@@ -713,7 +712,7 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 
 		severity = mce_severity(&m, mca_cfg.tolerant, NULL, false);
 
-		if (severity == MCE_DEFERRED_SEVERITY && memory_error(&m))
+		if (severity == MCE_DEFERRED_SEVERITY && mce_is_memory_error(&m))
 			if (m.status & MCI_STATUS_ADDRV)
 				m.severity = severity;