x86, mce: fix boot logging logic

The earlier patch to change the poller to a separate function subtly
broke the boot logging logic. This could lead to machine checks
getting logged at boot even when disabled or defaulting to off
on some systems. Fix that.

[ Impact: bug fix - avoid spurious MCE in log ]
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Reviewed-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/mce.h

@@ -137,6 +137,7 @@ DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);
 enum mcp_flags {
 	MCP_TIMESTAMP = (1 << 0),	/* log time stamp */
 	MCP_UC = (1 << 1),		/* log uncorrected errors */
+	MCP_DONTLOG = (1 << 2),		/* only clear, don't log */
 };
 extern void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 

arch/x86/kernel/cpu/mcheck/mce_64.c

@@ -239,9 +239,10 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 		 * Don't get the IP here because it's unlikely to
 		 * have anything to do with the actual error location.
 		 */
-
-		mce_log(&m);
-		add_taint(TAINT_MACHINE_CHECK);
+		if (!(flags & MCP_DONTLOG)) {
+			mce_log(&m);
+			add_taint(TAINT_MACHINE_CHECK);
+		}
 
 		/*
 		 * Clear state for this bank.
@@ -585,7 +586,7 @@ static void mce_init(void *dummy)
 	 * Log the machine checks left over from the previous reset.
 	 */
 	bitmap_fill(all_banks, MAX_NR_BANKS);
-	machine_check_poll(MCP_UC, &all_banks);
+	machine_check_poll(MCP_UC|(!mce_bootlog ? MCP_DONTLOG : 0), &all_banks);
 
 	set_in_cr4(X86_CR4_MCE);